Ken Livingstone was expelled from the Labour Party for five years last night for standing as an independent in the London mayoral election.
Jim Fitzpatrick, London Labour Party chairman, said that by handing over his nomination papers Mr Livingstone had expelled himself.
Hours earlier, Mr Livingstone was warned that if he won the contest he would face gridlock unless he worked with the party. Under the Greater London Act the mayor's budget can be blocked by two-thirds of the assembly. Labour would be likely to work with the Liberal Democrats and Tories to foil some Livingstone policies.
On the first day of the campaign Frank Dobson's running mate, Trevor Phillips, told Radio 4 that Mr Livingstone could face a tough time: "Were Ken Livingstone to become mayor he would have to ... satisfy a powerful Labour group that he ... knows what he's doing and that he's somebody we could work with. If he gets elected and he finds we are there holding him by the throat over the budget, then he may decide that he's going to have to eat his words and he will have to work with us."
Some Labour insiders were furious at Mr Phillips' apparant admission Mr Dobson would lose. But a Millbank spokesman said: "It was clear Trevor was answering a hypothetical question but he is campaigning for Frank to get elected."
The candidates who handed in nomination papers yesterday were: Geoffrey Clements (Natural Law Party), Susan Kramer (Liberal Democrats), Frank Dobson (Labour), Ram Gidoomal (Christian Peoples Alliance), Damian Hockney (UK Independence Party), Darren Johnson (Green Party), Ken Livingstone (independent), Steven Norris (Conservative).
Farm campaigners tried to nominate Winnie the Pig but the Department of the Environment said all candidates had to be "persons" and "over 21 years of age".