Gordon Brown will face a heavyweight Blairite challenge for the Labour leadership, according to reports.
As many as 10 cabinet ministers would back a challenge in the leadership contest expected within 12 months, said the Observer.
An unnamed source, reportedly involved in discussions between Blairite ministers, said that they were discussing uniting behind an 'anyone but Brown' candidate.
"Until the beginning of this week, most of us would have ended up supporting him because there was anyone else," said the source.
"Now almost for sure, because of his behaviour, there will be a serious challenge from someone within the cabinet and he's only got himself to blame.
"This week has been the cathartic moment. It's not about policy; the question is who has the character, the personal qualities. Gordon is his own worst enemy."
On Saturday Blair declined an opportunity to give the chancellor an endorsement as his successor.
In an interview with the News of the World Brown threw down the gauntlet to Blairite rivals for the job of Labour leader declaring: "I am happy for there to be a leadership contest. I think there should be.
"If people decide they want to stand when there is a leadership contest, whenever that happens, they should feel free to do so. I would welcome the open contest," he added.
Northern Ireland secretary Peter Hain gave strong backing to the chancellor, saying that "no-one could or should" defeat him in a leadership contest, which he predicted would come "probably sooner rather than later".
And the chancellor picked up a surprise endorsement from former US president Bill Clinton, who told the Sunday Telegraph: "I have known him since 1990 and I think he'd be a good prime minister."
