London Mayor Boris Johnson hit out at "trivial" and "hysterical" questions about his personal integrity and ambitions to be Prime Minister today.
In an interview with the BBC's Eddie Mair, a clearly uncomfortable Mr Johnson was forced to deny being a "nasty piece of work" and refused to discuss allegations about his private life.
The intense exchanges came after the Tory politician agreed to take part in an in-depth documentary about his life, due to be aired by the corporation tomorrow evening.
Mr Johnson suggested he had been effectively "blackmailed" into participating by respected journalist Michael Cockerell.
"It is like when the News of the World ring up and they say listen,you are going to be in this story. You can either cooperate or notcooperate," he said.
"I thought on the whole it was probably wiser given that it was going to happen anyway to try to say something rather than leave the field clear to put the boot in."
When Mr Mair said he wanted to "talk about you", the Mayor joked: "That's exactly what I am trying to avoid."
However, he appeared thrown as the interviewer grilled him on his sacking from The Times more than two decades ago for making up a quote.
"I mildly sandpapered something someone had said. It is very embarrassing, and I am very sorry about it," Mr Johnson said.
Mr Mair, standing in for Andrew Marr on his Sunday morning show, then pressed Mr Johnson over whether he lied to Tory leader Michael Howard about allegations of an extra-marital affair in 2004 - which resulted in his resignation as shadow arts minister.
"I never had any conversation with Michael Howard about that matter," the Mayor replied. "I do not propose to go into all that again. Why should I? I've been through it a lot. Why don't we talk about something else?"
Insisting that he was talking about "integrity", Mr Mair turned to a 1990 telephone conversation Mr Johnson had with one of his friends who was demanding the private address of a News of the World journalist.
A recording of the call suggested Mr Johnson had agreed to supply the details, even though his friend indicated he wanted to have the reporter beaten up for smearing his family.
Mr Johnson stressed today that "nothing eventuated" from the conversation, adding: "I think if any of us had our phone conversations bugged people say all sorts of fantastical things whilst talking to their friends."
Mr Mair said: "You are a nasty bit of work, aren't you?"
"All three things I would dispute... if we had a longer time I could explain that I think all three interpretations you are putting on these things are not wholly fair," an exasperated Mr Johnson replied.
Challenged to give a "straight answer" on whether he wants to be Prime Minister, the Mayor said: "What I want is for David Cameron to win this election which he deserves to do. In these circumstances it is completely nonsensical for me to indulge this increasingly hysterical conversation...
"What I want is to spend my time remaining as Mayor to do as well as I can as Mayor of London."
He went on: "I think people would rightly conclude that I don't want to talk about this subject because I want to talk about what should happen, which is that the Government deserves to win the next election.
"It is a measure of the trivialisation of politics that I thought I was coming on to talk about the Budget and housing in London, and you have...
"I do not mind all these questions about other stuff, but I think it is more important that we look at the things that are happening now in the economy and what the Government is doing to help.
"They don't care about phone conversations with my friends 20 years ago, they don't care about some ludicrous made up quote... what they care about is what is happening in the UK and which of the two parties has the best prospectus for recovery."
Asked if he was going to watch the documentary, Mr Johnson shot back ruefully: "I'm certainly not, not after what you have told me. I am not going to watch it."