The move will be controversial because Blunkett was forced to resign as home secretary last year when he was replaced by Clarke.

It will also add to the pressure on Clarke, who last week flew to Boston for a holiday in America despite the biggest manhunt in British police history and fears over a new terror campaign.

Many in Whitehall believe Clarke is not up to the job of running the war on terror and are unimpressed by his performance in the aftermath of the July 7 bombings.

Blunkett, who was home secretary in the wake of the September 11 attacks in 2001, has experience of overseeing anti-terrorism campaigns.

A senior Downing Street source said: “There has been a lot of fuss over Charles going on holiday, but we think he deserves one and David Blunkett will fill in over that brief period while he is out of the country. He obviously has a lot of experience in the area.”

Tony Blair, who is to go on holiday this week, has also given Hazel Blears, the Home Office minister, a role in the day-to-day running of the department. John Prescott, the deputy prime minister, will be in overall charge of government while Blair is abroad.

The source added: “Prescott is in charge, but Blunkett will have control over issues relating to the Home Office.”

Blunkett quit in December in a row over the fast-tracking of a visa for the nanny of Kimberly Quinn, his one-time lover.

Meanwhile, moves to expand Blair’s flagship unit responsible for tackling yob culture have been blocked by Prescott, a leaked letter seen by The Sunday Times reveals.

Downing Street wanted to take £50m from the deputy prime minister’s budget to give to the “respect unit”, which is run by Louise Casey, Blair’s “favourite” civil servant.

But Prescott rang round ministers to win their support then refused to budge. The letter from Blears, who is close to Blair, says that Prescott’s move is “extremely disappointing”, will “cause considerable problems” and “hamper” the government’s efforts to encourage responsible parenting and tackle problem families and poor school attendance.

The document, dated July 20, makes clear that Prescott’s refusal to give the funds will “cause considerable problems in bringing about the rapid change we are looking for”.

Last month The Sunday Times revealed that Blair had rebuked Clarke for failing to respond adequately to public concerns about yob culture.

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