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An election to the Assembly of London took place on June 10, 2004, along with the London mayoral election, 2004.
| Party | Seats | Gain |
| Conservative Party | 9 | 0 |
| Green Party | 2 | -1 |
| Labour Party | 7 | -2 |
| Liberal Democrats | 5 | 1 |
| UKIP | 2 | 2 |
The Assembly is elected by the Additional Member System. There are fourteen directly elected constituencies, nine of which were won by the Conservatives and five by the Labour Party. An additional eleven members were allocated by a London wide top-up vote, with the proviso that parties must win at least 5% of the vote to qualify for list seats. This latter rule prevented both the British National Party and the RESPECT Unity Coalition from winning a seat each.