On 1 May 2004 ten new member states joined the European Union. This article describes the party affiliations of the leaders of each member-state represented in the European Council from 1 May until the end of 2004. The list below gives the political party that each head of government, or head of state, belonged to at the national level, as well as the European political alliance to which that national party belonged. The states are listed from most to least populous. More populous states have greater influence in the council, in accordance with the system of Qualified Majority Voting.
