A former senior aide to President Bush claims that the White House deliberately mounted a dishonest propaganda campaign to sell the Iraq invasion to the US public, in the most damning insider account of the presidency so far.

Scott McClellan, who worked for Bush for seven years, including three as White House spokesman, brands the war a "serious strategic blunder" and "not necessary".

The scathing comments stunned Washington yesterday because the Bush team, until now, has had a reputation for intense loyalty to their boss. Republican strategists and former White House colleagues turned on McClellan, accusing him of writing the book for the money and asking why, if he felt as he had, he did not resign at the time. The White House expressed sadness and puzzlement.

McClellan's comments are from What Happened: Inside the Bush White House and Washington's Culture of Deception, to be published on Monday but excerpts of which appeared on the Washington-based Politico website.

On Iraq, McClellan says Bush and his advisers "confused the propaganda campaign with the high level of candour and honesty so fundamentally needed to build and then sustain public support during a time of war".

He accuses Bush and his advisers of being more interested in permanent campaigning for re-election in 2004 than what was best for the country.

McClellan admits he had misled the White House press corps, but had done so unknowingly and regrets that he "fell far short of living up to the kind of public servant I wanted to be". He also blames the US media for being too compliant and not sceptical enough in the run-up to war.

The White House does not normally comment on such books, but was forced to do so yesterday because McClellan had been such an integral part of the administration.

Dana Perino, the present White House spokeswoman, said: "Scott, we now know, is disgruntled about his experience at the White House. For those of us who fully supported him, before, during and after he was press secretary, we are puzzled. It is sad - this is not the Scott we knew."

She said Bush had been briefed on the book but she did not expect him to respond. "He has more pressing matters than to spend time commenting on books by former staffers."

But the book dogged Bush throughout yesterday on a trip to the west, fundraising for the Republican candidate in the November general election, John McCain, and to make a speech on Iraq. The account of how the White House manipulated public opinion is politically awkward for McCain, who must decide whether to distance himself further from Bush.

McClellan says in the 341-page book that the way Bush managed the Iraq issue from the summer of 2002 "almost guaranteed that the use of force would become the only feasible option". The US invaded in 2003.

The propaganda was part of the Bush administration's general approach to being in office. Bush wanted to achieve what his father failed to do, win a second term. McClellan says: "In the permanent campaign era, it was all about manipulating sources of public opinion to the president's advantage." Its aggressive stance involved "never explaining, never apologising, never retreating".

Bush has suffered this onslaught from one of the quieter members of his team. Although he had a prominent role as the White House's public front, McClellan tended to maintain a low profile at staff meetings. He gave no indication during his time as press secretary that he was disgruntled.

Part of the reason McClellan may have turned on his former boss is the Lewis "Scooter" Libby affair, which began with misleading information about Iraq and uranium, and ended with Libby being sentenced to jail, though he was released after an effective Bush pardon.

Karl Rove, who had been Bush's chief of staff and is now a commentator on Fox News, said yesterday that McClellan had been out of the loop on many issues and had never expressed his concerns while working for the administration.

Another former colleague, Frances Townsend, told CNN: "For him to do this now strikes me as self-serving, disingenuous and unprofessional."

Todd Boulanger, a Republican strategist, said: "If he was that outraged, why did he not resign?"

Inside stories

Among the first of the critics from inside the Bush administration was Paul O'Neill, who had been secretary to the Treasury. Although he did not write The Price of Loyalty, the book that appeared in 2004, he heavily briefed its author. In interviews to coincide with publication, he said that Bush at cabinet meetings was "like a blind man in a roomful of deaf people".

Richard Clarke, a national security adviser, wrote Against All Enemies the same year, in which he was critical of Bush administration's failure in counter-terrorism ahead 9/11 as well as the Iraq invasion.

Ari Fleischer, who was Bush's press secretary from 2001 to 2003, when he was replaced by McClellan, wrote a largely loyal account of his time in the job, Taking Heat, The President, the Press and My Years in the White House.

John Bolton, one of the administration's neo-conservatives who ended up as ambassador to the United Nations last year published Surrender Is Not An Option. He remains loyal to Bush, critical only in that he felt the administration did not go far enough, and was not tough enough with the UN or with Iran.