Former Labour leader Lord Kinnock said that Lord Mandelson had become a "caricature" of himself, as the one-time spin-doctor embarked on a publicity drive for his memoirs.

Lord Kinnock was critical of the book The Third Man questioning whether his former protégé was more interested in creating a sensation than adding to the historical record.

But Lord Mandelson denied reports that Tony Blair was "livid" about the book, saying he had been in touch with the former Prime Minister by text message since extracts began appearing in The Times.

The excerpts painted a picture of a dysfunctional relationship between Mr Blair and his Chancellor Gordon Brown.

The book quotes Mr Blair as describing his eventual successor as "mad, bad, dangerous and beyond redemption" and says he reneged on a promise to step down in Mr Brown's favour ahead of the 2005 general election.

Lord Mandelson has insisted the book painted a flattering picture of the two men who led the New Labour government.

And during an appearance on ITV1's This Morning, he copied out a message he had received from Mr Blair on his BlackBerry, which was later read out on air by presenter Phillip Schofield. It read: "I have specifically said to all who have asked that I am NOT angry!"

Mr Blair is due to publish his own memoir, entitled The Journey, later this year but was pipped to the post by his former right-hand man, who signed copies at a bookshop appearance in London on Thursday afternoon.

Earlier in the day, Lord Mandelson told BBC Radio 4's Today programme that the book "shows a very good and flattering picture of not just Gordon Brown and Tony Blair but others like me who helped them rescue the Labour Party from what it was in the 1980s".

Asked if he thought it was helpful to the party to publish his book now, Lord Mandelson insisted: "Yes, I do. I think you have to write these things when they are fresh in your mind and when they are relevant to a debate that's taking place."

He said he would continue to support the party financially and work for its success "until my dying day".

And he said Mr Brown's Administration - in which he became the effective second-in-command as First Secretary - would be judged by its response to the global banking collapse of 2008/09.

"I make clear, as far as Gordon is concerned, that the chief test of Gordon and his premiership was the way in which, and the success with which, he fought back against the financial crisis," said Lord Mandelson.

"I think that will be his chief legacy and chiefly how he is remembered as a Prime Minister."

Lord Kinnock told the BBC's Straight Talk: "The problem is with Peter, I really do believe - and I'm sorry about it in many ways, because he's got great capabilities, and he's been prepared to donate those capabilities to the cause of Labour - but the fact is, so much was said about him as, for instance, the Prince of Spin, and the Prince of Darkness, that he inhaled and he's actually come to believe that caricature of himself."

The former Labour leader, who gave Lord Mandelson his first senior job in the party as campaign coordinator for the 1987 election, questioned the circumstances of the production of the book.

The memoir "either has been written at breakneck, indeed a rate of genius velocity, or was being written many, many, many months before the general election", said Lord Kinnock.

And he added: "In all those circumstances, with this extraordinary gift of perfect recall that Peter seems to manifest in the book... I think that we have to wonder whether Peter's interest is in sensation and book promotion or faithful historical record."

David Cameron seized on Lord Mandelson's account of the Blair and Brown Administrations in the House of Commons on Thursday, when he mocked Labour for its "shambolic" time in government.

But the self-styled "Dark Lord" appeared to win over the queue of around 50 who came to pick up a copy from Hatchards, on Piccadilly, in central London.

Susan Warhurst, from Battersea, south London, was one of the first to leave the shop clutching a signed copy. The 65-year-old head-hunter said: "He was absolutely charming. I don't think he deserves the criticism. I think... good for him."

And Steve Carter, 53, from Church Broughton, Derbyshire, dismissed suggestions that the timing of the publication was calculated to damage Labour.

"It is very right for Mandelson but I don't think it'll make much difference for Labour," he said.

"They're a team who aren't a team at the moment. None of them can claim to have any moral high ground. There's no more damage to be done."