American Caesars: Lives of the US Presidents - from Franklin D Roosevelt to George W Bush

If you hate George W Bush and American neoconservatism, you will love this book. Taking Suetonius's Twelve Caesars for his template, the British historian Nigel Hamilton has written potted biographies of the 12 US presidents from 1933 to 2009, mostly with a pronounced anti-Republican bias. By the time he reaches "Dubbya", however, the bias has turned into what this reviewer considers to be a meaningless rant.

Greatness is accorded to Franklin D Roosevelt, Harry Truman, Dwight Eisenhower and John F Kennedy, with FDR rightly crowned as "the greatest Caesar of all". One might raise an eyebrow at Jimmy Carter being described as "the American Gandhi" who ran a stronger economy than his successor Ronald Reagan, or George Bush Sr being accused of having "made his pact with the Devil" in order to get elected, but none of the pen-portraits, not even those of Nixon and Reagan, comes close to the bile and loathing unleashed in the 41-page onslaught against the younger Bush.

Hamilton's distinguished life of Field Marshal Montgomery won the Whitbread Biography Award in 1981, but his descriptions of Bush, in my view, preclude him from being considered a serious commentator on contemporary American history. Casting historical objectivity aside, Hamilton describes Bush's "sneering contempt for those more intellectually gifted", and how he was "blinkered", "bewildered by adult life: spoiled, purposeless, self-destructive" and "ill-read to the point of near-illiteracy".

Bush's campaigning style was supposedly "cynical, relentlessly focused, manipulative, largely dishonest [and] negative" due to the baleful influence of Karl Rove, who is described as "short, ugly, prematurely balding and ambitious". Needless to say, all friends and supporters of Bush are written off as "cronies" or even, in Mafia terminology, as "capos".

Yet this portrait of Bush is backed up by next to no evidence. Virtually the only commentators quoted are Paul O'Neill, Richard Clarke and Scott McClellan, all of whom were sacked by Bush or have fallen out with and written denunciations of him. Some of Hamilton's accusations contradict themselves. For example, he accuses Bush and Rove of "pillorying" John McCain during the 2000 Republican primaries. Yet, in the next paragraph but one, he quotes McCain's campaign director stating (correctly) that the smear campaign against his candidate was "usually anonymous", and thus it was impossible to blame it on Rove rather than fanatics in the blogosphere.

Hamilton also alleges that Rove was involved with the Swift Boat Veterans who questioned John Kerry's war record in Vietnam before the 2004 election, which Rove has strongly denied. And the idea that, after a "palace coup" in the White House, Bush "ceded control of economic policy" to Rove is ludicrous, as are Hamilton's remarks about the wholesale "moral depravity of Rove's huge team". Equally, the assertion that Rove "evaded justice" over the "Scooter" Libby scandal, in which a CIA agent's identity was leaked, ignores the years of intensive investigation by no less tenacious a prosecutor than Patrick Fitzgerald, which concluded that Rove had no case to answer.

Hamilton ascribes Bush's acquiescence to the secret service insistence that he not return to Washington immediately after the World Trade Center and Pentagon attacks on 11 September 2001 to sheer "cowardice"; he also wrongly asserts that Dick Cheney, Bush's vice-president, "hid away" for weeks afterwards. He further accuses Bush and Cheney of "advocating something very close to treason" by promoting the invasion of Iraq, even though Bush gave the order to invade as commander-in-chief and both houses of Congress voted for the operation. The president's decision to go to war against Iraq was "infected" by "fevered madness".

The 11 September attacks "changed [Bush] into a buffoon", Hamilton asserts; Cheney wanted "a hopefully long and profitable war" because he "seemed mentally unbalanced". Meanwhile, Donald Rumsfeld, the secretary of defence, is written off as "self-preening and arrogant", his deputy Paul Wolfowitz as "fanatical" and Condoleezza Rice as "incompetent". Furthermore, the administration's "illegal" attempts to intercept domestic communications under the Patriot Act smacked, the author believes, of "the KGB at its worst". And the war on terror, he concludes, "turned the US into a failed state", in which "Orwell's nightmare of 1984 had come true". If anyone has a "cartoon-like view" of the world, it is Hamilton, not Bush.

Bush received 14 standing ovations during his address to the joint session of Congress after the 11 September attacks, but Hamilton considers that, on this occasion, the president "seemed overexcited, or on mood-enhancing medication". Once again, he offers not a shred of evidence for such a serious allegation. As an objective analysis of what was really going on in Washington in 2001-2003, this is worthless, even for those who opposed the war, because it reduces political motives, whether misguided or not, to a series of unproven psychological disorders. As history - as opposed to mere polemic - this book is bunk.

The author falls for every conspiracy theory going, stating that, "with the president's approval, Cheney's office ordered the false authentication of suspect secret intelligence"; that the CIA knew for certain that there were no weapons of mass destruction in Iraq; that Tony Blair was "Bush's poodle", rather than a true believer in the project from the start; and that "America", rather than a handful of renegade Appalachian warders, was responsible for the abuses of inmates at Abu Ghraib jail.

For all that he hubristically equates his book with those of Lytton Strachey and Suetonius, and for all that his biography of Monty was a first-class piece of work, Hamilton this time has allowed personal loathing to obliterate his historical judgement.

American Caesars: Lives of the US Presidents - from Franklin D Roosevelt to George W Bush
Nigel Hamilton
Bodley Head, 608pp, £25

Andrew Roberts's "The Storm of War: a New History of the Second World War" is newly published in paperback by Penguin (£10.99)