Ken's arrogance cost him Mayor's job says Jowell

"There is nothing that alienates people more than what they see as the arrogance of power," she told a fringe meeting at Labour's annual conference in Manchester.

Ms Jowell, who oversaw Labour's campaign, also suggested the former mayor's length of service could have put voters off re-electing him. "You have to assume that in modern politics longevity works against you," she added. Her remarks underline a belief held by many that Mr Livingstone should not be allowed to stand again.

And Joy Johnson, Mr Livingstone's former communications director, has told how investigations by the Evening Standard "appeared to confirm that [City Hall] grant-giving was influenced by favouritism" - the first significant admission about the Lee Jasper scandal by one of Mr Livingstone's inner circle. She said Mr Livingstone's decision to "hang on" to Mr Jasper, his race adviser, despite allegations of cronyism, was "wrong", "doomed" and "a mistake".

At the meeting, a string of senior London Labour figures voiced criticism of Mr Livingstone's mayoral campaign. Steve Reed, leader of Lambeth council, accused the campaign of sending "mixed messages" about Conservative candidate Boris Johnson. "With one hand we said he was a buffoon and with the other we said he was a dangerous extremist," said Mr Reed. "Both things cannot be true, and the voters concluded that neither was true."

Writing in the British Journalism Review Ms Johnson said: "When someone is in the eye of the media storm - on this occasion, Lee Jasper - resignation must be swift. Our reasoning, that resignation would look like an admission of guilt, was a mistake."

The consequence of the Jasper affair was, Ms Johnson said, "an inability" for the Livingstone campaign to get back on the front foot.

"With a barrage of negative stories arising from leaked emails that appeared to confirm grantgiving was influenced by favouritism, we were operating against a backdrop of hostile stories," she added.

Ms Johnson also said the Evening Standard's billboards had caused "incalculable damage" to the Livingstone campaign. However, she admitted some stories were "legitimate".