Senior Labour figures pleaded for calm yesterday as the imminent publication of Peter Mandelson's memoirs, The Third Man, provoked a fresh round of party infighting.
The book, to be published this week, will detail the intrigue and manoeuvring for position between Tony Blair and Gordon Brown. Mr Blair's version of events will follow in September.
After Lord Mandelson protested in a pre-publication interview that Mr Brown had been "badly served" by his aides, Charlie Whelan, Mr Brown's former press secretary, turned his fire on the peer. Mr Whelan claimed the former business secretary ran the "worst general election campaign in Labour's history" and accused him of being more interested in writing his book than helping the party to win votes.
Andy Burnham, a leadership contender, added to the row when he said: "I saw at close quarters some of this egotistical infighting which, quite frankly, I believe damaged the Labour Party. We spent our time attacking each other when we should have been attacking the Tories."
Lord Prescott, the former deputy prime minister, led a series of prominent Labour figures urging the party to lower the temperature and look forwards rather than rake over the past.
Speaking on BBC1's Andrew Marr Show, he said: "We lost the election when we started attacking each other internally about Brown and Blair – now being reiterated in Peter's book."
Harriet Harman, Labour's acting leader, said memoirs "have their place" but insisted: "We are now where we are and our job is to hold the Government to account.'
Hazel Blears, a former cabinet minister, said the party needed to stay on track. "What I don't want to happen is with the publication of anybody's memoirs that we take some of the morale out of the Labour Party."
Lord Mandelson's book is published on Thursday. He has said that the timing was intended to help the candidates for the Labour leadership, as later publication would drag the victor "back into the past".
Reports have suggested Mr Blair is resentful at having been beaten into print by his old sparring-partner. Friends of the former prime minister said the claims were "simply untrue".