Mr Ken Livingstone will take to the high streets and town halls of the capital in a bid to mobilise ordinary voters in an independent campaign for London mayor which will pit him against the power of "machine" politics.
The left-wing MP was feeling the full force of New Labour's Millbank machine last night as his confirmation that he will stand against the party's official candidate, Mr Frank Dobson, unleashed a torrent of criticism and abuse. He was suspended from the party by the general secretary, Ms Margaret McDonagh, using "delegated powers" pending a full inquiry and rubber-stamping by the party's national executive.
In any event it was understood Mr Livingstone would be automatically expelled once he had submitted nomination papers for the May election.
An angry Mr Dobson branded Mr Livingstone "a liar" and a danger to London, while the Prime Minister, Mr Blair, repeated his view that Mr Livingstone's election as mayor would be "disastrous in terms of business, crime and transport" in the capital.
Announcing his decision, Mr Livingstone acknowledged he was breaking his previous promise not to leave the party, saying: "I offer no weasel words of equivocation and I apologise." But he added: "What I do not intend to do is take any lectures from those who have set new standards in ballot-rigging."
Asked later at a press conference whether Londoners could trust him, he said: "They have seen the commitments I have given, they have weighed that against the way in which Labour conducted its mayoral selection. They will choose which actually is the greater crime."
But the Deputy Prime Minister, Mr John Prescott, said: "It would be hard for a government or an Assembly to work with Ken Livingstone when he's shown that you simply can't trust his word."
Mr William Hague joined the fray amid claims by the Tory candidate, Mr Steve Norris, that he was "delighted" by Mr Livingstone's decision and confident he could "come through the middle" and win the election on the back of a split Labour vote.
The Tory leader said: "This leaves the Dobson campaign dead in the water and the Labour Party split down the middle. Frank Dobson was always a Downing Street stooge who never really wanted the job, and today we know he'll never get it."