Ken Livingstone’s judgment and credibility came under heavy fire last night when his closest aide suddenly quit after further revelations about his conduct.

A City Hall spokesman confirmed that Lee Jasper’s departure was connected to claims that he channelled £100,000 of taxpayers’ money to projects run by a woman he bombarded with sexually charged e-mails. Mr Jasper, who was already suspended from his job as race adviser after a string of allegations, failed to disclose to the Mayor of London his relationship with Karen Chouhan, the company secretary of the 1990 Trust and director of the Black Londoners’ Forum.

In his resignation letter, Mr Jasper blamed the “racist nature of a relentless media campaign” for his decision. His departure is a significant blow for Mr Livingstone, who for months stood by his long-serving adviser, saying in December there was an audit record of “every penny” that had been spent by the London Development Agency.

The move means Mr Jasper will not now have to answer questions before the London Assembly today.

Mr Jasper’s departure came after the London Evening Standard reported that he sent a string of messages to Mrs Chouhan. In one to the 50-year-old mother of three who he calls “darling”, he reportedly wrote: “I love thee [sic] ankles, legs, thighs, bum and belly, arms, head and brain. But most of all I love you in a flaming red sari, bangles, chains or failing that in a bikini!”

Days after sending the e-mails, the 1990 Trust was given £65,000 by City Hall after a recommendation by Mr Jasper. Mr Jasper failed to disclose his relationship with Mrs Chouhan or any interest in any organisation to City Hall, according to the Standard.

Mr Jasper denied any impropriety.

Contacted yesterday by The Times, Mrs Chouhan said: “I have known Lee for 22 years, nothing was going on, it was banter. It wouldn’t surprise me if that kind of language had been used [in the e-mails],” she said. She did not comment on Mr Jasper’s resignation.

A spokesman for the GLA said: “No evidence has been presented for the criminal allegations presented by the Evening Standard.

“However, Lee Jasper has stated that in light of material published today that he has tendered his resignation. The mayor has accepted it.”

In his resignation letter, Mr Jasper said: “It has become clear that a number of matters which are not of first importance in London are being used to distract from the crucial questions in the election campaign.

“The racist nature of a relentless media campaign [against me] and the consequent effects on myself and family have placed an intolerable strain on all of us. I have decided to put a stop to this by tendering my resignation.”

However, Atma Singh, the mayor’s former adviser on the Asian community, disputed his claims about the nature of coverage in the press. “This is nothing to do with racism. The media has every right to question what the mayor and the mayor’s officers are doing with public money.”

Mr Livingstone’s opponents in the race to be the next mayor said that Mr Jasper’s resignation raised questions about the mayor's judgment.

Boris Johnson, the Tory candidate, said: “The resignation of one of the Labour mayor’s most senior and trusted advisers is further proof that Ken Livingstone has had his day.

“He has repeatedly said he is directly responsible for the actions of his advisers and he should take Jasper’s place tomorrow and answer the questions that Jasper won’t.

“Otherwise, Londoners can only conclude he is arrogant and out of touch. Londoners deserve to know where their hard-earned cash has gone.”

The Tories have called for a code of conduct for the mayor’s advisers.

Brian Paddick, the candidate for the Liberal Democrats, said: “The resignation raises serious questions about the mayor’s claims that there is nothing wrong with his administration. Increasingly, black Londoners are asking me to get in and clean up City Hall, saying I am the only candidate they trust.

“This proves that the controversy surrounding Lee Jasper is about incompetence and the improper use of taxpayers’ money, not race.”

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