Political party affiliation in the United Kingdom

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Membership and affiliation within political parties in the United Kingdom are governed by various eligibility criteria and behavioural expectations. Most parties restrict membership to individuals who meet age and citizenship requirements, share the party's core principles, and agree to abide by its constitution and rules. Members are typically prohibited from joining or supporting rival political organisations or from standing against officially endorsed candidates. In addition to full membership, some parties offer forms of associate or supporter status, which allow limited participation without the obligations of full membership.

Contents

Whilst these rules help preserve party integrity and cohesion, they also define the extent to which individuals can engage with political life in the UK. Supporters without formal membership may contribute to campaigning or fundraising, but generally have fewer rights in internal decision-making or leadership elections.

History

Membership of political parties has been in decline in the UK since the 1950s, falling by over 65% from 1983 (4 per cent of the electorate) to 2005 (1.3 per cent). [1] In 2022, 1.5% of the British electorate were members of the Conservative Party, Labour Party, or the Liberal Democrats. [2] Typically party affiliation allows an individual to support only a single party. However, two notable exceptions to this are: the Co-operative Party which permits its members to also have membership of the Labour Party and the Social Democratic and Labour Party (SDLP); and the Scottish National Party, which permits membership of Plaid Cymru.

According to the UK Parliament website sourced from a report by Olympic Britain, [3] during the 1950s there were 2.8 million members of the Conservative Party and 1 million Labour Party members. In the years after 1945 until the early 1990s, supporters of the Socialist and Cooperative parties and trade unions linked with the Labour Party increased the overall Labour Party movement by 5 to 6 million, from which point they[ vague ] began to fall and currently[ when? ][ citation needed ] number about 3.5 million.

Despite being founded in 1900, the Labour Party did not begin keeping track of its membership until 1928. On the other hand, the Conservative Party rarely releases their total membership statistics; additionally, there are no clear membership statistics for the Conservative Party before 1945. It is estimated that between World War I and World War II, membership levels were around 1.5 million; however, exact numbers are unknown.

Current membership

PartyCurrent membershipRegistered supportersDateRegion
Labour Party 309,000 [4] —February 2025United Kingdom
Reform UK 260,000 [5] —9 October 2025United Kingdom
Green Party of England and Wales 175,000 [6] —23 November 2025England and Wales
Conservatives 123,000 [7] —July 2025 (date reported)United Kingdom
Liberal Democrats 60,000 [5] 23,000 [5] 31 December 2024United Kingdom
Scottish National Party (SNP)56,011 [8] —June 2025Scotland
Your Party 55,000 [9] —November 2025United Kingdom
Advance UK 37,000 [10] —September 2025United Kingdom
Co-operative Party 13,430 [11] —31 December 2024United Kingdom
Sinn Féin 10,000+ [12] —September 2024Northern Ireland
Plaid Cymru c.10,000 [13] —30 August 2022Wales
Scottish Greens 9,000 [14] —12 November 2025Scotland
Workers Party of Britain 7,469 [15] —January 2025Great Britain
Alba Party 5,002 [16] —26 March 2025Scotland
UK Independence Party (UKIP)3,888 [17] —31 December 2020United Kingdom
Freedom Alliance 3,040 [18] 2024Scotland
Socialist Workers Party 2,504 [19] 6,000 [19] 2023Great Britain
English Democrats 2,500 [20] —2015England
Social Democratic Party (SDP)2,000 [21] —January 2021United Kingdom
Communist Party of Britain (CPB)1,808 [22] —31 December 2023Great Britain
Independent Oxford Alliance 1,740 [23] 12 August 2025England
Gwlad 645 [24] —March 2025Wales
British National Party 500 [25] —2015United Kingdom
Official Monster Raving Loony Party 457 [26] —31 December 2024United Kingdom
National Liberal Party 328 [27] 2023Great Britain
Socialist Party of Great Britain 300 [28] —2023Great Britain
Wessex Regionalists 21 [29] —2021England

Labour Party

In the Labour Party's 2020 leadership election 490,731 people voted, of whom 401,564 (81.8%) were full members, 76,161 (15.5%) had affiliated membership and 13,006 (2.6%) were registered supporters. The registered supporter class was abolished in 2021. [30]

Conservative Party

The Conservative Party's membership was revealed as 131,680 at the end of the 2024 Conservative Party leadership election.

Liberal Democrats

Lib Dem membership increased sharply after the confirmation on 18 April 2017 of the 8 June 2017 general election. [31] Membership again increased sharply in the period before and after the two elections of May 2019, for the UK Councils and the European Parliament.

Scottish National Party

There was a huge surge in membership after the 2014 Scottish independence referendum, prior to which the SNP had just over 25,000 members. [3] Membership peaked at over 125,000 in August 2018, [4] before falling by tens of thousands in the final years of Nicola Sturgeon's leadership. [32]

Reform UK

Membership increased by over 50% from 31,000 to 45,000+ in the eight days after Nigel Farage announced he would be returning to lead the party. [33]

Green Party of England and Wales

On 31 December 2015, the Green Party of England and Wales announced its membership as 63,219, its highest known membership up to that date. [34] On 19 September 2025, it was revealed that the party had reached over 75,000 members. [35] Less than a month later, on 9 October 2025, the party tweeted it had reached 95,000 members, [7] a day after announcing it had surpassed 90,000. [36] This "surge" has been accredited to their new leader, Zack Polanski, who was elected a month prior. [37] On 12 October 2025, the party reached a record-breaking 100,000 members, marking an over 45% increase since Polanski was elected, [38] and as of 27 October 2025, the Green Party has over 150,000 members. [39]

Co-operative Party

Though the Co-operative Party stands joint candidates with the Labour Party, their membership bases are independent (members have the option of joining both parties).

Enforcement

There are few high-profile cases of membership criteria enforcement and as such tend to happen under exceptional circumstances.

2015 Labour leadership election

During the 2015 Labour party leadership election it emerged that 260 former candidates from the Green Party, Left Unity and the Trade Union and Socialist Coalition had attempted to become registered supporters, but were subsequently blocked from voting. [40] Shortly before this, it was revealed that Conservative MP and former junior minister Tim Loughton had been caught applying to become a registered Labour supporter, subsequently claiming that his intention was to "blow the gaff on what a complete farce the whole thing is". [41] Veteran Labour MP Barry Sheerman also joined calls for the election to be "paused" over the fears of infiltration by other parties. [42] The Labour Party told representatives of the four candidates at a meeting on 11 August that 1,200 members and supporters of other parties had been excluded and a further 800 were under investigation. [43] Harriet Harman at the time admitted that as many as 100,000 people may be blocked from voting. [44]

The number of those rejected eventually reached 56,000, [45] around 9.1 per cent of the 610,753 considered eligible to vote at the start of the contest. [46] According to the party, 45,000 of those were rejected for not being on the electoral register. [47]

Labour also confirmed that it would cancel supporters' votes after they had been cast, if it was found that they were members of other parties. [48] A number of high-profile individuals have been blocked from voting, including Marcus Chown, [49] Jeremy Hardy, Douglas Henshall, [50] Ken Loach, [49] Francesca Martinez, [50] Mark Serwotka, [51] Pete Sinclair, [52] Mark Steel, [53] Luke Wright [54] and Toby Young.

Andrew MacKinlay, a former Labour MP, further alleged that Labour was attempting to rig its own leadership election against Corbyn; [55] a view shared by Jeremy Hardy. [56] Such allegations became known to the media – and particularly Corbyn supporters – as the "Labour Purge", with #LabourPurge trending on Twitter. [55] Claims of such a "purge" of Corbyn supporters were rejected by Harman who insisted that the exclusion processes were impartial to candidates. [57] Scottish newspaper The National printed a page-long satirical cartoon speculating further vote-rigging by Labour's leadership. [58]

Brexit

Conservative peer Michael Heseltine had the whip removed in 2019 after expressing his intention to vote Liberal Democrat. [59] Conservative policy appears to make such expulsions discretionary, [60] despite threats from Conservative Campaign Headquarters. [61]

Tony Blair's support for pro-remain parties led to questions about why he had not been expelled from the Labour Party. [62] Alastair Campbell was expelled from the Labour Party after saying he voted for the Liberal Democrats in the 2019 European election. [63] Many Labour members came out in support of Campbell using the hashtag #expelmetoo, reporting that they had similarly voted for the Liberal Democrats or other remain parties. [64]

Criteria for membership

PartyMembership restrictions
Conservative Party "open to all who share its objects and values and who undertake to be bound by this Constitution"

"Membership of the Conservative Party is not compatible with Membership of or association with any other registered political party" [65]

Labour Party "are not members of political parties or organisations ... declared ... ineligible for affiliation to the party."

"[Must not stand in] opposition to a Labour candidate"

"[Must not support] a political organisation ... who stands against an official Labour candidate" [66]

Liberal Democrats "Open to all persons who agree with its fundamental values and objectives without discrimination as to age, ethnic origin, religion, disability, gender or sexual orientation."

"Membership may be revoked [due to] standing against the candidate of the Party"

"Membership may be refused [due to] membership of another political party in Great Britain" [67]

Democratic Unionist Party (DUP)
Scottish National Party (SNP)"I endorse the aims of the Party"

"A member may not contest or be a member of any organisation [deemed to be a Political Party] contesting elections in opposition to the Party" [68]

Sinn Féin "only residents of Ireland are eligible for membership" [69]
Plaid Cymru "I endorse the aims of the Party and agree to abide by its constitution. I am not a member of any other political party active in Wales" [70]
Co-operative Party "must also be a member of a recognised co-operative"

"...agree to accept the rules and to promote the policy and values of the Co-operative Party. ...not a member of any political Party other than the Labour Party or the Social Democratic and Labour Party." [71]

Social Democratic and Labour Party (SDLP)
Alliance Party Disclose if you/I "am/was a member of another UK or Irish political party" and give the name of the party.
Green Party of England and Wales "Membership is open to any person who subscribes to the object of the Party, and is not already a member of another political party, other than Green Parties abroad, subject to clause 4(vii) below."

"No member of the Party may be a candidate for any other party in an election for any level of government and no member of another party may be a candidate for The Green Party in any such election except in cases of joint candidacies. No member of the Party may stand as an independent candidate against properly selected Green Party candidate(s). No member may campaign for any candidate standing against a properly selected Green Party candidate." [72]

Scottish Greens "I accept and will further the aims of the Scottish Green Party, and am not a member of any other political party except a sister Green party" [73]
Green Party in Northern Ireland "not a member of any other political party." [74]
Ulster Unionist Party (UUP)
Traditional Unionist Voice (TUV)Support for the principles of Unionism, Independence from the Republic of Ireland and Family values [75]
UK Independence Party (UKIP)"open to any natural person who shares the objectives and core beliefs of the Party"

"[Membership shall be revoked if a member] joins another political party ... or any organisation membership of which the NEC has declared to be incompatible"

"[Membership shall be revoked if a member]has set up or has aided and abetted the setting up of another political party"

"[Membership shall be revoked if a member]stands against a UKIP candidate in any election" [76]

"I am not and have never been a member of Hope not Hate, Antifa, Communist League, Left Unity, Extinction Rebellion or Just Stop Oil." [77]

Communist Party of Britain "Apply to join the Communist Party by paying an initial online registration fee (£6).

Once you have registered an online application you will be contacted by a representative of your local Party branch for a membership interview. New members are only admitted to the Party on acceptance by their local CP organisation. If your application to join the Communist Party is refused, you will be refunded your online registration fee, with £1 retained to cover administration costs.

Please note if you apply to join and withdraw your application, your application fee is not refundable."

"You must be aged 16 or above to join the Communist Party."

Official Monster Raving Loony Party "One year’s membership to The Loony Party is £15".

Provide a "Loony Name".

Reform UK "Membership of the Party shall be open to any natural person who shares the objectives and core beliefs of the Party and who agrees to abide by this Constitution and any Rules which may from time to time be made by the Board [...]"

"Notwithstanding anything in Article IV of this Constitution, the Board may from time to time make Rules concerning the refusal of or exclusion from membership of persons or classes of persons whose admittance to membership of the Party would, in its opinion, be inimical to the interests of the Party."

"The Party Chairman (or, in his absence, his designated deputy) shall, without reservation or qualification, be entitled, to refuse to admit any person to membership." [78] [79]

See also

Notes and references

  1. ↑ John Marshall: Membership of UK political parties; House of Commons, SN/SG/5125; 2009, page 6. https://www.parliament.uk/commons/lib/research/briefings/snsg-05125.pdf Retrieved 5 January 2012
  2. ↑ Burton, Matthew; Tunnicliffe, Richard (31 August 2022). "Membership of political parties in Great Britain". UK Parliament. House of Commons Library. Retrieved 24 December 2023.
  3. 1 2 "Scottish referendum: 'Yes' parties see surge in members". BBC News. 22 September 2014.
  4. 1 2 Green, Daniel (5 February 2025). "Membership down 11% since election as Labour loses a member every 10 minutes". LabourList. Retrieved 11 June 2025.
  5. 1 2 3 Catt, Helen (9 October 2025). "Liberal Democrat membership has halved in 5 years, figures show". BBC News. Retrieved 9 October 2025.
  6. ↑ Wahab, Rustam (23 November 2025). "Zack Polanski's Greens Smash 175,000 Members as Party Surges to 17% in New Poll". HuffPost UK. Retrieved 26 November 2025.
  7. 1 2 Holl-Allen, Genevieve (23 July 2025). "Tory membership falls under Badenoch". The Daily Telegraph. Retrieved 25 July 2025. At the time of the leadership election last year, the Tories had 131,000 members but this has since fallen to 123,000.
  8. ↑ Cochrane, Angus; Sim, Philip (21 August 2025). "SNP facing financial challenge as membership drops". BBC News. Retrieved 22 August 2025.
  9. ↑ Methven, Steven (1 December 2025). "Inside Your Party Conference: Is This Farewell to Corbynism?". Novara Media . Retrieved 2 December 2025.
  10. ↑ "How the world's richest man is boosting the British right". Sky News. Retrieved 17 November 2025.
  11. ↑ "the co-operative party board report & annual accounts 2024" (PDF). party.coop. Co-operative Party. 31 December 2024. Retrieved 22 August 2025.
  12. ↑ McQuinn, Cormac (27 September 2024). "Sinn Féin to examine 'limited' success in increasing 'activist' membership". The Irish Times. Retrieved 4 November 2025.
  13. ↑ Burton, Matthew; Tunnicliffe, Richard (30 August 2022). "Membership of political parties in Great Britain" (PDF). UK Parliament House of Commons Library. Retrieved 18 September 2022.
  14. ↑ Jackson, Lucy (12 November 2025). "Scottish Greens pass 9000 members as support 'skyrockets'" . The National. Retrieved 12 November 2025.
  15. ↑ "Workers party of Britain - Special Congress 2025" (PDF). Archived from the original (PDF) on 26 February 2025.
  16. ↑ Brown, Hannah (26 March 2025). "MacAskill wins Alba leadership following Salmond's death" . The Herald. Retrieved 4 May 2025.
  17. ↑ "United Kingdom Independence Party Limited (a company limited by guarantee) report and accounts 31 December 2020". Electoral Commission. 31 December 2020. Archived from the original on 14 August 2023. Retrieved 1 July 2025.
  18. ↑ https://search.electoralcommission.org.uk/Api/Accounts/Documents/26469
  19. 1 2 "Delusions of 'official optimism'". Weekly Worker. 21 March 2024.
  20. ↑ Eaton, George (14 January 2015). "Green Party membership on course to overtake Ukip's". The New Statesman. Archived from the original on 22 January 2015. Retrieved 24 January 2015.
  21. ↑ Liddle, Rod (24 January 2021). "My SDP has definitely caught the public mood. Now all we need is some votes". The Times . Archived from the original on 7 July 2021.
  22. ↑ "Report And Accounts For The Year Ended 31 December 2022". Communist Party of Britain – via Electoral Commission.
  23. ↑ https://search.electoralcommission.org.uk/Api/Accounts/Documents/27299
  24. ↑ "Statement of account details (Gwlad, 2025)". Electoral Commission. Retrieved 5 August 2025.
  25. ↑ Bolton, Doug (17 April 2015). "General Election 2015: The BNP has almost vanished from British politics". The Independent.
  26. ↑ OFFICIAL MONSTER RAVING LOONY PARTY: Statement of Accounts: 1st Jan – 31st Dec 2024 (PDF). 2025. p. 2.
  27. ↑ "National Liberal Party - True Liberalism". search.electoralcommission.org.uk.
  28. ↑ "Tiny socialist party amasses £2.6m in reserves". 25 August 2023 – via www.bbc.com.
  29. ↑ "Wessex Regionalists". search.electoralcommission.org.uk.
  30. ↑ Burton, Matthew; Tunnicliffe, Richard (30 August 2022). "Membership of political parties in Great Britain" (PDF). House of Commons Library. UK Parliament. Retrieved 25 March 2023.
  31. ↑ "Lib Dem Membership tops 100,000 after snap election call". BBC News . 24 April 2017. Archived from the original on 4 May 2017. Retrieved 24 April 2017.
  32. ↑ Meighan, Craig (16 March 2023). "SNP reveals huge membership losses as 30,000 people leave party". STV News. Retrieved 16 March 2023.
  33. ↑ Horton, Harry (11 June 2024). "Reform UK membership grows 50% in week since Farage announces run for parliament". ITV News. Retrieved 11 June 2024.
  34. ↑ "The Green Party of England and Wales – Report and Financial Statements – Year ended 31 December 2015". The Green Party of England and Wales. p. 5. Archived from the original on 28 August 2016. Retrieved 24 August 2016.
  35. ↑ Walker, Peter (19 September 2025). "Green party membership surges after public split between Corbyn and Sultana". The Guardian. ISSN   0261-3077 . Retrieved 19 September 2025.
  36. ↑ "Liberal Democrat membership has halved in 5 years, figures show". BBC News. 9 October 2025. Retrieved 12 October 2025.
  37. ↑ "Green Party membership overtakes Liberal Democrats under Polanski". Sky News. Retrieved 12 October 2025.
  38. ↑ Party, Green (12 October 2025). "Green Party membership surges past 100,000 as polls show record support". Green Party. Retrieved 12 October 2025.
  39. ↑ Elliott, Frankie (27 October 2025). "Jeremy Corbyn and Zarah Sultana admit losing data of 20,000 Your Party members in portal mix-up". LBC . Retrieved 27 October 2025.
  40. ↑ Wintour, Patrick; Perraudin, Frances (7 August 2015). "Labour leadership election: 260 members of rival parties ask to vote". The Guardian.
  41. ↑ Perraudin, Frances (5 August 2015). "Tory caught signing up as Labour supporter wanted to expose vote 'farce'". theguardian.com . Retrieved 11 August 2015.
  42. ↑ Walker, Carole (10 August 2015). "Labour contest should be 'paused', MP Barry Sheerman says". BBC News. Retrieved 10 August 2015.
  43. ↑ Mason, Rowena (11 August 2015). "Labour leadership contest: campaign teams summoned over ballot concerns". The Guardian.
  44. ↑ Nickerson, James (25 August 2015). "Labour leadership race: Acting leader Harriet Harman admits up to 100,000 members could be purged from vote". City A.M.
  45. ↑ Blanchard, Jack (26 August 2015). "Labour Party rejects 56k bids to vote in leadership contest to calm fears of Tory infiltration". Daily Mirror.
  46. ↑ "Over 600,000 people will be able to vote in the Labour leadership contest". LabourList. 12 August 2015.
  47. ↑ "Number of voters in leadership contest revised down to 550,000". LabourList. 25 August 2015.
  48. ↑ "Labour is going to cancel some supporters' leadership votes after they've been cast". The Independent. London.
  49. 1 2 "The Labour Purge Is Underway, And They've Banned Me From Voting Corbyn (IMAGE)". Scriptonite Daily. Archived from the original on 11 June 2017.
  50. 1 2 Glaze, Ben (20 August 2015). "Genuine Labour supporters barred from voting for leader due to 'robust' checks". Daily Mirror.
  51. ↑ "Labour leadership: Mark Serwotka of PCS union has vote rejected". BBC News. 26 August 2015.
  52. ↑ "Labour supporters claim leadership vote 'purge'". Channel 4 News. 20 August 2015.
  53. ↑ Allegretti, Aubrey (13 August 2015). "Mark Steel's Ban From Vote in Labour Leadership Election Prompts Raging 'Entryism' Debate". Huffington Post.
  54. ↑ Nickerson, James (20 August 2015). "Labour leadership race: Now Labour is blocking genuine party members from leadership vote". City A.M.
  55. 1 2 Riley-Smith, Ben (21 August 2015). "'Labour purge' is deliberate attempt by party to stop Jeremy Corbyn winning, former MP claims". The Daily Telegraph. London.
  56. ↑ "Jeremy Hardy: 'Labour trying to rig leadership election'". BBC News. 21 August 2015.
  57. ↑ Payne, Sebastian (25 August 2015). "Harriet Harman: we are not purging Corbyn supporters". The Spectator.
  58. ↑ "Not Waving But Purging". thenational.scot. Archived from the original on 25 September 2015.
  59. ↑ "European elections 2019: Heseltine loses Tory whip over Lib Dem vote". BBC News. 20 May 2019. Retrieved 13 July 2019.
  60. ↑ Peretz, George (1 May 2019). "Are Conservative members who endorse the Brexit Party at risk of expulsion?". Prospect. Retrieved 13 July 2019.
  61. ↑ Pearson, Allison (1 May 2019). "Why I will be voting for the Brexit Party". The Daily Telegraph. Retrieved 13 July 2019.
  62. ↑ May, Josh (30 April 2017). "John Prescott questions why Tony Blair has not been expelled from Labour". Politics Home. Retrieved 13 July 2019.
  63. ↑ Mason, Rowena (28 May 2019). "Labour expels Alastair Campbell from party". The Guardian. Retrieved 13 July 2019.
  64. ↑ Tobin, Olivia (29 May 2019). "#expelmetoo: Furious members who voted against Labour in European elections dare party to kick them out after Alastair Campbell's expulsion". Evening Standard. Retrieved 13 July 2019.
  65. ↑ "Constitution of the Conservative Party (Page 10)" (PDF). Retrieved 6 September 2014.
  66. ↑ "Labour Party Rule Book (Page 9)" (PDF). Retrieved 6 September 2014.
  67. ↑ "The Constitutions of the Liberal Democrats" (PDF). www.libdems.org.uk. Retrieved 24 June 2016.
  68. ↑ "CONSTITUTION OF THE SCOTTISH NATIONAL PARTY" (PDF). www.snp.org. Retrieved 6 September 2014.
  69. ↑ "Join Sinn Féin". www.sinnfein.ie. Retrieved 8 September 2014.
  70. ↑ "Join Plaid Cymru -The Party of Wales today". partyofwales.org. Retrieved 6 September 2014.
  71. ↑ "The Rule Book – Co-operative Party". The Co-operative Party. 2022. Retrieved 9 July 2023.
  72. ↑ "Our Constitution". greenparty.org.uk. Retrieved 30 November 2025.
  73. ↑ "Join the Scottish Green Party" (PDF). www.scottishgreens.org.uk. Retrieved 6 September 2014.
  74. ↑ "Membership Form". www.greenpartyni.org. Retrieved 8 September 2014.
  75. ↑ "Application for membership" (PDF). www.tuv.org.uk. Retrieved 8 September 2014.
  76. ↑ "The Constitution". www.ukip.org. Retrieved 6 September 2014.
  77. ↑ "Join Online". join.ukip.org. Archived from the original on 5 January 2024. Retrieved 5 January 2024.
  78. ↑ "Join - Reform UK as a Member" . Retrieved 4 October 2025.
  79. ↑ "Reform UK Constitution 2025" (PDF). Retrieved 4 October 2025.
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