The Conservatives have accused Gordon Brown of "causing mayhem" in the Cabinet amid further reports of rifts with the prime minister and other senior ministers.

Interviewed on Sunday, Brown refused to deny there was any agreement between the two most powerful men in the government that at some stage Blair would step down in favour of his chancellor.

Brown told BBC1's Breakfast with Frost programme that he had a "very strong working relationship" with Blair, adding: "He's doing an excellent job. He will stay as prime minister and that's the right thing to do."

But pressed further, he declined to comment on any deal.

"What Tony Blair and I have said to each other really is a matter for us," he said. "What Tony Blair and I talk to each other about is something very private."

The latest suggestion of divisions at the very top of the government followed reports that health secretary Alan Milburn was angered that he received only a day's notice of Brown's pledge, made in his pre-Budget statement last week, to rule out private financing of the NHS.

Milburn was said to be considering a range of reforms that will now have to be scrapped. These included allowing patients to pay for luxuries during their hospital stays, which could have generated extra revenue for the health service.

The chancellor and the health secretary are also said to be at odds over ear-marking specific taxes to pay for the NHS, a policy also backed by Labour Party chairman Charles Clarke.

Brown told the BBC that a debate about linking taxes with services "will go on", but described pure hypothecation as "not acceptable".

"People...want to see that the money they are paying is linked to an improvement in service and that it is a debate that will go on. But pure hypothecation, which is this linking of one tax to perhaps the fate or fortune of the economic cycle, is really not acceptable," he said.

The chancellor also said on Sunday that he wouldn't raise income taxes to pay for the national health service.

On the day Tony Blair backed increases in general taxation to pay for the health service, Brown said the he would not raise the basic or higher rates of income tax but declined to comment on whether other taxes may rise.

The chancellor said the government would keep its manifesto promise not to raise income taxes. "We will keep every promise that we made at the general election, every promise that is in our manifesto," he said.

Brown said the government would also keep its promise not to extend the scope of VAT, but avoided saying whether the ceiling for national insurance contributions would be raised.

"I made my pledges on the election in income tax and VAT. I made it absolutely clear at the election that no chancellor going into Budgets will make specific pledges on other issues. That is a matter for debate and discussion," he said.

Brown also rejected suggestions by Charles Clarke that the government could back euro membership even if it was only a "50-50 call".

The chancellor said there would be no watering down of the government's five economic tests. "These tests have got be met and that is why people will want to know that the results of those tests are clear and unambiguous," he said.

The latest reports prompted the Conservative Party chairman, David Davis, to describe Brown as "causing mayhem around the Cabinet table".

"The government is lurching from crisis to crisis and Gordon Brown is at the centre of all the troubles. According to the Sunday papers he is at war with half of his Cabinet colleagues and today on BBC Breakfast with Frost he slapped down both Charles Clarke, the Labour Party chairman and the prime minister."

"Gordon Brown believes he has a private agreement to take over the job of PM. His overweening ambition is wrecking the government but perhaps more importantly the chancellor's sulky tantrums are distracting ministers from doing the real job of rescuing Britain's lamentable public services," said Davis.