Cameron criticised after taking £13,000 payment for his role in 'candid' biography

David Cameron has been criticised after being paid £13,000 for his part in a new biography which will 'define him ahead of the next election'.

Doubts have been raised about the book's independence because the Tory leader received several thousand pounds from the author for giving 'wide ranging and candid interviews'.

Labour MPs also called on Mr Cameron to declare any payment to the Commons standards watchdogs.

A spokesman for the Tory leader confirmed on Sunday that he had received the payment. The money has been donated to charities, including one for disabled children, she said.

Cameron on Cameron, written by the editor of GQ magazine Dylan Jones, is billed by its publishers as the book to 'settle the question of whether David Cameron has got what it takes to lead the country'.

It has received lukewarm reviews and been criticised for failing to ask critical enough questions.

'As is usual in situations like this, both David and I were paid an advance by the publishers and we will split the royalties, if any,' Mr Jones told the Sunday Telegraph.

However, a spokesman for HarperCollins, the publisher, said: 'We didn't pay any money to David Cameron.'

Sources said the Tory leader's share had instead come through Mr Jones's agent.

Political biographers were surprised by the deal, claiming it would have undermined the author's objectivity.

'I can't imagine a serious biographer ever offering a subject money,' said Anthony Seldon, who wrote books on Tony Blair and Sir John Major.

'I would never have dreamt of doing it.'

Another distinguished writer Anthony Howard, who declined to write a book on Barbara Castle when the Labour stalwart demanded a split of the proceeds, called the agreement 'reprehensible'.

Labour minister Tom Watson called the deal 'cosy' and added: 'How can this biography either be impartial or critical if the subject is being paid. At the very least it raises those questions.'

Co-authors: Cameron, with wife Samantha and Dylan Jones at the book launch

According to the book's blurb from HarperCollins, 'Jones teases out the details of Cameron's positions on the big issues... for an unprecedented view into a politician's world and a document of practical use in our democracy'.

Topics covered include the Iraq war, the UK-U.S. relationship, education and immigration. Mr Cameron also discusses his marriage and disabled son.

'When the project was first discussed, David made clear that any fee would go to charity and that is the case.'

Sources also pointed out the book was not a biography but a series of interviews and that Mr Cameron is listed as a co-author.

Media darling: David Cameron has received attention from other magazines including Time

Labour backbencher John Mann said it was still 'appropriate' for Mr Cameron to declare the money to the standards commissioner for inclusion in the register of members' interests.

'The donation to charity is very worthy but this is a significant sum of money,' he said.

'Of course, it should be declared straight away. It is very important that people in his position are seen to be acting entirely within the rules.'

Fellow Labour MP Kevan Jones said: 'If he has received income and hasn't declared it the commissioner, he should and he should explain why he hasn't.'

Under Parliamentary rules, MPs must declare within four weeks 'outside employment, professions and sources of remuneration (of more than one per cent of a Member's salary a year)', around £700.

Mr Cameron's spokesman insisted: 'The payments have been fully and properly declared.'

At the swanky Mayfair launch party last week, the Tory leader, 41, and wife Samantha, 37, were pictured dancing awkwardly.

Cameron caught in Christmas card controversy

Mr Cameron was at the centre of further controversy yesterday after it emerged that a poignant photograph of him cradling one of his children was being used by his wife's up-market stationery firm to sell its Christmas cards.

The picture shows the Tory leader gazing lovingly into the eyes of his son Ivan , who suffers from cerebral palsy.

It was posted on the Smythson website to promote cards which can be personalised with customers' own images, but has since been removed.

Mr Cameron's wife Samantha, who has been creative director at Smythson's for 11 years, was said to be 'mortified' by the blunder.

She had apparently donated three pictures to be used on the company's website in 2004.

'It is a totally different situation now from when it was first provided for use,' a Smythson spokesman said.

She said the error went initially unnoticed because Mr Cameron's face is partly obscured by shadow.

The Tory leader has been accused of exploiting his family for political gain after inviting TV crews into his home to film his family having breakfast.

A party spokesman said: 'David wasn't aware that these photos had been used but appreciates this was a genuine error. Sam had forgotten all about them and is mortified. This is a mistake and not in any way an attempt to use Cameron family pictures to promote Smythson.'

Smythson counts the Queen, Claudia Schiffer and Damien Hirst among its customers. The personalised cards, which cost from £409 for 100, feature holly borders and come with envelopes.