London Mayor Boris Johnson has hit out at "trivial" and "hysterical" questions about his personal integrity and ambitions to be Prime Minister.
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 on Monday evening.
Mr Johnson suggested he had been effectively "blackmailed" into participating by respected journalist Michael Cockerell. 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."
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. "I never had any conversation with Michael Howard about that matter. I do not propose to go into all that again," the Mayor replied.
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.
"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," Mr Johnson said.
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."
He went on: "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."