Cameron's personal attack on Brown: 'That strange man in Downing Street'

He used a newspaper interview and bitter exchanges in the Commons to ram home Tory criticisms about the Prime Minister's "dithering" and "bad judgment".

The Tory leader's sustained attacks on Mr Brown's character marked an escalation in their increasingly personal battle.

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Mr Cameron is enjoying a strong lead in the polls but is under pressure to put his party beyond reach at the next election.

He also used an interview in The Times to make an unashamed appeal to the middle classes over education, expressing sympathy for those who bend the rules to get their children into religious schools.

Mr Cameron is trying to exploit what he believes are growing signs of weakness in Downing Street as Mr Brown's relaunch struggles to get noticed.

Last night No 10 announced the "immediate" departure of Tom Scholar, the Prime Minister's civil service chief of staff, after only seven months in the job.

Awkwardly for Mr Brown, he has asked Jeremy Heywood, the former head of Tony Blair's private office, to return.

Currently running the Cabinet Office, he becomes the first Permanent Secretary to run the Prime Minister's office.

It follows the appointment of former City spin doctor Stephen Carter to head No 10's political operations.

The news emerged after a day that saw Mr Cameron step up the intensity of his attacks on the Premier.

Asked about the public finances, he replied: "I am being very careful because if you ask about anything else, that strange man in Downing Street will cook up an enormous package of Tory spending cuts."

He claimed the Prime Minister failed to prepare for the global economic downturn by allowing borrowing to escalate.

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"We have not fixed the roof while the sun was shining," he said.

Later in the Commons he accused Mr Brown of an "error of judgment" for taking Virgin boss Sir Richard Branson - who is one of two bidders for Northern Rock - on a business trip to China and India.

He said: "Last week you were in favour of nationalisation. You get a tough time at Prime Minister's Questions, get on a plane with Richard Branson and drop the whole plan."

He added: "You've gone from prudence to Del Boy without even touching the ground."

Asked about evidence that some parents are "finding religion" to get their children into religious state schools, Mr Cameron told The Times: "I think it's good for parents who want the best for their kids.

"I don't blame anyone who tries to get their children into a good school."

Afterwards Mr Cameron's office stressed he did not approve of dishonesty.

"But he does agree with parents doing the best they can to get into good school," an aide said.

Mr Cameron is waiting to hear if his four-year-old daughter has got a place at a Church of England school in Kensington, West London.