Ed Miliband has come under pressure to reveal what he knew about the systematic smear campaigns Gordon Brown's former spin doctor has admitted orchestrating to destroy the careers of Labour rivals.
Damian McBride has laid bare sensational details of the methods he used to see off potential threats, including former home secretaries John Reid and Charles Clarke, at a time when he was determined to ensure Mr Brown succeeded Tony Blair as Prime Minister.
In his book Power Trip, serialised in the Daily Mail, the former special adviser reveals details of the infighting and media manipulation in the Labour party in the run-up to Mr Blair stepping down in 2007.
Former Cabinet minister Dame Tessa Jowell said she was "sure" the Labour leader, who was a close ally of the former prime minister, had been aware of disgraced special adviser Damian McBride's activities - a claim that was quickly seized on by Tories.
In the extracts Mr McBride wrote: "Labour, Conservative or Liberal Democrat; Ministers, MPs or advisers; if they'd ever shared their secrets with colleagues in Westminster, the chances were that I ended up being told about them, too. Drug use; spousal abuse; secret alcoholism; extra-marital affairs. I estimate I did nothing with 95% of the stories I was told. But, yes, some of them ended up on the front pages of Sunday newspapers."
Mr McBride said he acted "out of loyalty and devotion" for Mr Brown, the then Chancellor of the Exchequer, who he said was unaware of his attempts to discredit rivals.
Ardent Blairite Dame Tessa told BBC News the revelations were "truly shocking" and condemned the "awful, evil influence of people like Damian McBride".
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."
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."
Deputy Prime Minister Nick Clegg said the book showed that Labour was "riven" by factionalism. "I think the challenge for Ed Miliband, strangely enough, is that he hasn't really ever had to address that, but I think it's brewing there," he told LBC 97.3.