Labour achieved 80% of its aims, Lord Mandelson says
Lord Mandelson has defended Labour's time in office, saying the party had "achieved 80%" of its aims.
He told the BBC that Tony Blair had wanted to "go further" than Gordon Brown in making public service reforms, but "we have to look at the positive".
Lord Mandelson also reacted to criticism of his memoirs by Labour leadership contenders, saying they "hadn't read the book".
Three candidates have urged Lord Mandelson to leave politics.
His memoirs, called The Third Man, have been serialised this week, discussing in some depth the disputes during Labour's years in power between the key figures in the party, particularly Mr Brown and Mr Blair.
But Lord Mandelson told BBC One's Andrew Marr Show there had been a "creative tension".
He added: "If it hadn't been, we wouldn't have been able to rebuild the Labour Party into New Labour and win all the elections that we did and follow with considerable achievements."
The peer, who led his party's negotiations with the Liberal Democrats following the hung parliament at the last general election, added that he had thought Labour had a "less than 50% chance" of forming a coalition.
He said: "I don't think the arithmetic stacked up, whoever was to partner the Labour Party."
Moving on to the Iraq war, Lord Mandelson said the US defence secretary had "swept aside" planning for the post-conflict situation and that "we paid a heavy price for that".
Lord Mandelson said he regretted the behaviour of the Labour government following the publication of the 2004 Hutton Report over the death of weapons expert Dr David Kelly.
This exonerated ministers but was critical of the BBC, leading to the resignation of the then director-general, Greg Dyke.
Lord Mandelson said: "It was more becoming of the government just to accept that in a more modest... way than was the case."
Labour Leadership contender Diane Abbott told BBC One's The Politics Show that Lord Mandelson had been a "malign" influence on British politics.
She said: "There's no doubt that the other candidates have been clamouring to dissociate themselves from it [the book], but many of them were proteges of Peter Mandelson."
David Miliband has called excerpts of Lord Mandelson's book published in the Times newspaper "destructive and self-destructive".
His brother and rival candidate, Ed Miliband, said: "I think this is sad and damaging to Peter, not just to the Labour Party."
Another contender, Andy Burnham, said: "Peter loves the spotlight but it's time to leave the stage."
Lord Mandelson said he had spoken to some of the candidates, who had told him "they hadn't read the book".
Meanwhile, left-wing Labour MP Jon Cruddas told Sky News: "There's a lot of blood-letting and personalities and there's a danger that our legacy is weakened."