David Cameron has been criticised for accepting almost £20,000 for giving interviews as part of a book about him.

The Tory leader received the money, which he is donating to charity, for taking part in Cameron on Cameron by Dylan Jones, the editor of GQ magazine. Biographers and opposition politicians expressed surprise that he received money for the book, which has received lukewarm reviews and been criticised for failing to ask hard-hitting questions.

The publisher, HarperCollins, could also face criticism for suggesting that the book is an evenhanded assessment of the Tory leader. The synopsis on its website says that the book “set out to answer these questions in a series of wide-ranging and candid interviews that will define David Cameron ahead of the next election – and for years to come”.

Tory sources emphasised that the book was never billed as a biography and point out that the arrangement is common in this type of work. HarperCollins, which prints the book under its Fourth Estate label, lists Mr Cameron as a co-author on its website.

A spokesman for the Conservative Party said: “Before the interviews began the terms were very clear. David insisted that any money would be going direct to charity.”

Mr Cameron disclosed that he was receiving money at the launch event last week. He told guests: “It is supposed to be going to charity, but I think I will be hiving off a little bit to buy Steve Hilton a suit,” referring to his adviser, who was in a tracksuit.

Mr Jones said later: “As is usual in situations like this, both David and I were paid an advance . . . and we will split the royalties, if any.”

The Tories last night confirmed that Mr Cameron had received payment, and suggested that it would be split between three charities, including one for disabled children. They said that the payment had not yet appeared in the Register of Members’ Interests because it was recent. MPs must declare payments within four weeks.

A spokesman for HarperCollins, which is owned by News Corporation, parent company of The Times, said: “Our contract was with Dylan Jones. We didn’t pay any money to David Cameron.”

A source disputed that HarperCollins was unaware of his payment, but said that the fee was received through Mr Jones’s agent, rather than through the publisher.

It has not stopped criticism from the publishing and political worlds.

Anthony Seldon, the biographer of Tony Blair and Sir John Major, said: “I can’t imagine a serious biographer ever offering a subject money. I would never have dreamt of doing it.”

Kevan Jones, a Labour MP, said: “How can this biography either be impartial or critical if the subject is being paid?”

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