Former Labour minister Ivan Lewis has attacked former Gordon Brown spinner Damian McBride's "ugly" approach to politics, as McBride's confessions about the divisions at the heart of the last government threatens to consume the party's conference in Brighton.
In his new book, serialised in the Daily Mail, McBride admitted to leaking a story to the press in 2008 that Lewis had been "pestering" a female civil servant. A charge he denied.
Speaking at a fringe event at the Labour Party conference on Sunday evening hosted by the Blairite Progress group, Lewis, now shadow international development secretary, hit back at Brown's former enforcer.
"The style of politics that Damian McBride came to represent belongs in the dustbin of history and it must never rear its ugly head in our party again," he said to applause.
Lewis also backed Ed Miliband's claim that he had raised concerns about McBride with Brown. Lewis said: "He was one of the few who expressed concerns about that style of politics at the time. He will show zero-tolerance for that type of politics."
Speaking at the same event, shadow foreign secretary Douglas Alexander also took aim at McBride, telling activists he had "paid a price" for opposing him.
"What Damian McBride represented wasn't just the way politics is or just some briefing, it was destructive, divisive and deeply damaging to our party," he said.
"I and others paid a price for opposing that style of politics at the time but I am absolutely clear today that we must - and we will - back Ed Miliband in his resolve to never, ever again allow that kind of conduct or that kind of culture to take hold within our party."
In his book, McBride accused Alexander of knifing his sister Wendy by encouraging Brown to ditch her as leader of the Scottish Labour Party - an accusation he has denied.
Alexander told a separate event in Brighton on Sunday evening that he had urged Brown to fire someone, but "it was Damian McBride".
"That might explain the way that he briefed against me then and writes against me now. I was always a supporter of my sister and I was never a supporter of Damian," he said.
McBride hit back at Alexander on Twitter. "Some brass neck," he said having learned of the Labour front bencher's comments. "When Douglas poses as the voice of probity and unity, I draw the line," he said.
Alexander and Lewis made the comments at a rally held by the internal Labour group Progress - which is associated with Tony Blair.
The event heard from a series of senior Labour politicians, including Tessa Jowell, shadow defence secretary Jim Murphy and shadow education secretary Stephen Twigg, who urged unity.
Lewis, despite his attack on McBride, said it was the "duty" of every MP to focus on the issues that mattered to voters rather than internal politics. He insisted of any internal-Labour divisions: "We're not competing tribes."
He said: "They will never forgive us and never take us seriously if we fan the flames of division and turn inwards on ourselves or focus on our past."
Labour's vice-chairman Michael Dugher also tried to dismiss the characterisation of continued Blairite and Brownite factions within the party as "bollocks".
And John Woodcock, the Barrow and Furness MP and vice-chair of Progress, said the "ego-fuelled divides or the Blair/Brown years must never, ever return".
However much of the rally was occupied with celebrating Progress' survival, after an attempt by some elements of the left wing of the party to have it banned.
Lewis said: "I'm delighted Progress has not been outlawed because for the first time in my life I would have had a criminal record."
And amid a debate about the direction Miliband is taking the party, shadow cabinet members insisted that the party had to remain in the centre ground in order to win in 2015.
Shadow energy secretary Caroline Flint warned the party could not win a majority if it did not "win back" people who had voted Tory in 2010. "We can talk to our core vote," she said. "But we won't win in the south".
In an apparent nod towards the power of the unions over Labour, Woodcock said: "To win again, Labour must always put the British people first ahead of any special interest group, no matter how powerful or sometimes how close to home."
And in the face of attacks from the coalition that Labour plans to borrow too much and drive up the deficit, shadow work and pensions secretary Liam Byrne said the party had to set out a "credible plan" to grow the economy and be "realistic about money".