Labour leader Ed Miliband has been forced to deny any involvement in attempts to smear opponents amid claims that "damaging" emails could have been sent by him to one of the key figures in a plot to attack senior Tories.
The potential link between Mr Miliband and Derek Draper, who was behind a proposed Labour-supporting political gossip website, is among the latest allegations in a memoir from Gordon Brown's former spin doctor.
The drip-feed of claims from Damian McBride threatens to overshadow the Labour Party conference despite Mr Miliband's efforts to seize the initiative by announcing he would scrap the "bedroom tax" if he wins the 2015 general election.
In the latest extracts from Mr McBride's memoir Power Trip, being serialised in the Daily Mail, the former member of the Brown inner circle s uggests Mr Miliband could "have problems" if any emails to Mr Draper became public.
Labour sources denied that Mr Miliband had any involvement in the proposed Red Rag website, which ultimately brought about the downfall of Mr McBride, and the book does not suggest he was involved.
A spokesman for Mr Miliband said: "Ed was not involved in any plan to smear or spread lies about opponents. Any suggestion he was is totally untrue."
Mr McBride was forced to resign as Mr Brown's head of strategy in 2009 after he sent Mr Draper emails containing scurrilous gossip and lies about Conservative MPs as planning for Red Rag took shape.
Details of the Red Rag plan were revealed in leaked emails, and Mr McBride tells how he questioned Mr Draper about how it could have happened.
He quotes Mr Draper as saying he had been "extremely naive" with his password, which had been "pretty obvious".
Mr McBride said he asked: "What's the worst anyone could have found if they've been in your emails?"
Mr Draper said there were a number of Labour ministers "who would have problems because of things they've written to me".
Mr McBride said the names given by Mr Draper were: "Peter Mandelson - definitely, James Purnell - definitely and Ed Miliband - probably."
In the book Mr McBride warns: "If somewhere sitting in a drawer, waiting to be deployed before the next election, are any damaging emails from Ed Miliband to Derek Draper, then I'd suggest this needs some attention."
Mr Miliband has come under pressure to reveal what he knew about the systematic campaigns Mr Brown's former spin doctor has admitted orchestrating to destroy the careers of Labour rivals during the bitter infighting of the New Labour years.
Ardent Blairite Dame Tessa Jowell told BBC News she condemned the "awful, evil influence of people like Damian McBride" and was "sure" Mr Miliband was aware of his activities.
She added: "I don't think it's damaging for Ed Miliband. I'm sure he knew that this was going on. He was actually away a lot of the time.
"But the strength of Ed Miliband has been to say that that is the past, we are not going back to that and that I am not going to preside over a parliamentary party or a Labour party that allows this kind of bad and malign behaviour and I think that has been a very important part of building confidence."
Conservative MP Henry Smith said: "After the revelations from Tessa Jowell, Ed Miliband must now tell us what he knew about McBride's Labour smear campaigns."
The latest revelations from Mr McBride, including claims that as prime minister Mr Brown suggested troops might have to be deployed to keep order in the event of a total collapse of the banking system, came just hours after Mr Miliband had unveiled his eyecatching policy decision to scrap the coalition Government's "hated bedroom tax".
Labour insists the £470 million expected to be saved by the welfare reform could instead be covered by closing "shady" tax loopholes.
Ahead of the party's conference in Brighton Mr Miliband told the BBC: "Our conference is all about how we tackle the cost of living crisis hitting so many families. We are going to be showing during the course of this week how we are going to do that.
"We are starting by showing how we are going to abolish the bedroom tax by ending boardroom tax loopholes that this Government has allowed.
"I think that's a fair choice, it's going to help disabled people, it's going to help some of the people in the greatest hardship in our country."
He added: "This is about an unfair welfare change which is hitting people hard, which is hitting the disabled, and it's not even going to work. It's unfair and it could cost the taxpayer money as well.
"Because what we are seeing with the bedroom tax is people potentially being evicted from their homes, and it won't even save what the Government said it was going to save."
Shadow chancellor Ed Balls, like Mr Miliband a member of the Brown inner circle during the New Labour years, admitted there was a "macho" style of politics within the party at the time, but denied knowing about Mr McBride's campaigns.
He told The Times: "The period up to 1997 and after, yes, it was macho, I look back on that as a time we were young and inexperienced."
He said both Mr Brown and Tony Blair allowed it to happen but "it was a mistake and it was damaging to the Government".
Mr Balls insisted that both he and Mr Miliband had learnt the lessons of that period.
"Both of us have lived through years of corrosive personality tensions about who should be leader. Both of us have completely decided together that that is absolutely not where we are going again."
He distanced himself from Mr McBride, telling the newspaper he was not aware of the spin doctor's briefing operations against ministers.
"No, I didn't know," he said. "He was a law unto himself, it now seems."
Mr Balls revealed that he turned down an invitation by Mr Brown, as prime minister, to have a Cabinet-level job in Downing Street "second guessing" chancellor Alistair Darling.
The then children's secretary refused to become an "Alan Walters figure", a reference to Margaret Thatcher's economic guru whose influence unsettled Nigel Lawson and led him to quit as chancellor.
Mr Balls told the newspaper: "I was asked to see Gordon in Downing Street. He said: 'Leave the children's department, come back to Downing Street, be in the Cabinet and be part of it here and part of the strategic planning.' I said I couldn't do it, I wanted to help but I couldn't go back to those days.
"It would be impossible for me to do that job, that I wasn't going to be the Alan Walters figure in the heart of Downing Street, second-guessing the chancellor and I said I wouldn't do it. He never understood that for the subsequent two-and-a-half years it was difficult. He never felt that I was willing to do what he wanted."