President Bush veered “terribly off course” and pursued an aggressive “propaganda campaign” which obscured the truth in selling the Iraq war to the American public, according to his former White House press secretary.

In a new book, Scott McClennan said the likely verdict of history would be that “the decision to invade Iraq was a serious strategic blunder”, adding: “War should only be waged when necessary, and the Iraq war was not necessary.”

He accused Mr Bush of managing “the crisis in a way that almost guaranteed that the use of force would become the only feasible option” — while also failing to be “open and forthright” about the reasons for military action.

The White House spokeswoman Dana Perino said yesterday: “Scott, we now know, is disgruntled about his experience in the White House. For those of us who fully supported him before, during and after his time as press secretary, this is puzzling and sad. This is not the Scott we knew.”

Mr Bush, she added, had more pressing matters with which to deal than comment on Mr McClennan’s 341-page book, entitled: What Happened: Inside the Bush White House and Washington’s Culture of Deception. Indeed, there was astonishment in Washington yesterday that a man who served Mr Bush with intense loyalty for seven years should have turned on the President with such venom.

In his time as press secretary Mr McClennan was regarded widely as a likeable, if somewhat hapless, member of a tight inner circle of advisers — the so-called “Texas mafia”. When he left the White House in 2006 Mr Bush even promised that there would come a time when they would be both “rocking on chairs in Texas, talking about the good old days” as he assured his departing aide: “I will feel the same way then that I feel now [and] that I can say to Scott, ‘Job well done’.”

Karl Rove, formerly the President’s chief strategist, suggested that Mr McClellan, 40, had been transformed into someone who “sounds like a left- wing blogger”. “If he had these moral qualms, he should have spoken up about them. And frankly I don’t remember him speaking up about these things,” he said.

Mr McClennan stopped short of saying that outright lies were told about Iraq, adding that he still admired the President’s intelligence and charm. He claimed, though, that the way Mr Bush routinely made decisions on gut instinct, demonstrated a “lack of inquisitiveness [and] a detrimental resistance to reflection”.

He described a political strategy that left the White House in permanent campaign mode, refusing to acknowledge mistakes or cede an argument. The first occasion he saw Mr Bush convincing himself — for reasons of “political convenience” — to believe something which “probably was not true” was in 1999 when he overheard Mr Bush, then the presidential candidate, apparently unable to recall ever taking cocaine.

“’We had some pretty wild parties back in the day, and I just don’t remember,’” Mr Bush is reported to have said. Mr McClennan wrote: “How can someone simply not remember whether or not they used an illegal substance like cocaine? It didn’t make a lot of sense.”

The book, released before its scheduled publication on Sunday by a Washington bookstore which inadvertently sold advance copies to reporters, is scathing about the Administration’s “out of touch” response to Hurricane Katrina in 2005 and criticises many of its most senior members. The Vice-President, Dick Cheney, is described as “the magic man \ always seemed to get his way”, while the Secretary of State, Condoleezza Rice, was “somehow able to keep her hands clean, even when the problems related to matters under her direct purview”.

Mr McClennan also made fresh claims on how the name of the CIA operative Valerie Plame came to be made public, claiming that aides such as Lewis “Scooter” Libby, Mr Rove and, possibly, Mr Cheney, deceived him and the President about the leak.

Speaking out

— “War should only be waged when necessary, and the Iraq war was not necessary.”

— On Bush's continuous campaign strategy: “Never explaining, never apologizing, never retreating ... never reflecting, never reconsidering, never compromising. Especially not where Iraq was concerned.”

— On the leak of CIA operative”s Valerie Plame's identity: “I had allowed myself to be deceived into unknowingly passing along a falsehood. It would ultimately prove fatal to my ability to serve the President effectively. The top White House officials who knew the truth - including Rove, Libby and possibly Vice-President Cheney - allowed me, even encouraged me, to repeat a lie.”

— On his time as press secretary: “I spent countless hours defending the Administration from the podium in the White House briefing room. Although the things I said then were sincere, I have since come to realise that some of them were badly misguided.”

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