Chancellor Gordon Brown only gave his backing to the invasion of Iraq at the 11th hour, according to his former Cabinet colleague David Blunkett.
Gordon Brown reportedly withheld backing until the last minute
The Guardian and Daily Mail, which are serialising Mr Blunkett's memoirs, said the book reveals the "chaos" and rows in Tony Blair's war cabinet.
Ministers were said to have asked Mr Blair searching questions about the lack of post-war planning in Iraq.
And Mr Brown allegedly questioned the point of going to war cabinet meetings.
The chancellor complained that he learned more about what was going on from the media, according to Mr Blunkett's account.
He finally only gave his support for the invasion of Iraq "at the 11th hour", the newspapers said.
Mr Blunkett was said to be in despair over the behaviour of US President George Bush and his administration - a view he was said to share with other members of the Cabinet.
He was also reportedly very critical of US Defence Secretary Donald Rumsfeld, complaining that he wielded too much influence during Mr Bush's first term in the White House.
The extracts published earlier on Monday concentrate on the events surrounding Mr Blunkett's resignation as Home Secretary in 2004 over the fast-tracking of a visa application for his then lover, Spectator publisher Kimberly Quinn.
In diaries, which he dictated into a tape recorder each night, Mr Blunkett vividly describes the anguish he felt after the affair became public and his career fell apart.
At one point he said: "Even I am beginning to doubt myself. I think I am going mad. I know the facts, but these are then widely presented as being completely untrue."
Later he added: "Virtually every day for the next 15 months was either a nightmare or an anticipated nightmare, with massive collateral damage to family and friends."
He described how, in the middle of the media storm, he was damaged by the publication of his biography by author Stephen Pollard which reported a series of highly critical remarks he had made about Cabinet colleagues.
"I felt the whole world opening up beneath me. I recognised that this was a rapier, not a pinprick," he said.
"For the rest of my life, I will regret speaking to Stephen Pollard. It was the biggest mistake of my years in frontline politics."
Some colleagues, such as Margaret Beckett and Charles Clarke, were forgiving. However, Deputy Prime Minister John Prescott was not.
Describing the scene at a 2004 Christmas dinner, days before his first resignation, he said: "Everyone who cared for me said that they had never seen John Prescott look at me with such hatred and bitterness."