If "chillaxing" was an Olympic sport then David Cameron, would win a gold medal, according to a new biography of the prime minister.

His ability to separate his private life from his professional life is seen as an asset by some friends, and by others as a sign of complacency in the midst of a double dip recession.

The book, Cameron: Practically a Conservative, describes how on a weekend Cameron may practice his game with a tennis machine he calls "the Clegger", after the deputy prime minister. Later on, he would cook dinner, have a few glasses of wine and sing My Way on his personal karaoke machine.

But the prime minister's ability to relax can cause problems, such as when last year's riots intruded upon his summer holiday in Tuscany and he was slow to realise the enormity of the situation.

With Britain in recession and the Conservatives falling in the polls, Cameron's leisure habits have increasingly been criticised by both his Conservative and Labour opponents as a sign of complacency.

Authors, Francis Elliot and James Hanning also chart the loss of faith in Cameron's relationship with his chief policy guru, Steve Hilton, who has just taken a year's sabbatical from his work at Downing Street to teach at a California university.

Cameron and Hilton have been friends for 20 years but as the concepts they worked on, such as the "big society", have failed to make an impact, so their professional attachment has waned, the authors write.

Hilton, who has been much satirised for his unconventional approach and use of jargon, believes Cameron has become too focused on power rather than pushing through radical change, according to the book, which is being serialised in the Times.

In their detailed portrait of the prime minister at work and leisure, the authors also detail how Cameron maintains an even temper when infuriated by pen-clicking, phone checking and transport delays. If he does lose his temper, he is quick to apologise, according to the biography.

The prime minister's relaxed appearance is not arrived at easily, according to the biography.

The book quotes an ally describing Cameron's ability to chill out and relax. "If there was an Olympic gold medal for 'chillaxing', he would win it. He is capable of switching off in a way that almost no other politician I know of can. The political mind is still working. He tends to get up early, look at the Sunday papers, check a few things online, the phone might ring and he'll deal with that.

"But then he doesn't go back to obsessively checking the computer or rewriting the speech, or worrying about what [rightwing journalist Matthew d'Ancona] really means. It's: 'I have absorbed the information, I have taken an action, I have asked Ed Llewellyn to do such and such, I will now go into the vegetable patch, watch a crap film on telly, play with the children, cook, have three or four glasses of wine with my lunch, have an afternoon nap, play tennis'."

For Michael Gove, the education minister and a close friend of Cameron, the prime minister's ability to relax is a rare quality. "He is the model of how to have a clear divide between the world of work and then relaxation, so you can clear your mind. There are very few people who have such a finely developed capacity to do that," he is quoted as saying.

The book also claims that while New Labour was seen to rely to heavily on political pollsters, Cameron has a predilection for political betting websites. The authors write that he does not bet but enjoys examining politics through the eyes of bookmakers.

Labour backbencher John Mann said: "People across the country will be concerned that while Britain was heading for a recession made in Downing Street, David Cameron was concentrating on 'chillaxing'.

"The prime minister should be totally focused on a plan for jobs and growth rather than playing computer games on his iPad."