Downing Street has denied that the chancellor is using the top-up fees issue to further his leadership prospects.

A spokesman for the prime minister said the chancellor had given his full public support to the policy.

"From the prime minister down the government is doing all it can to get this legislation through," he said.

With the rebels still confident of securing the 81 votes they need to block the Higher Education Bill on Tuesday, Brown is seen as integral to the prime minister's chances of avoiding defeat.

Interviewed on GMTV on Sunday, the chancellor called on backbenchers to support the government, but refused to confirm whether Tony Blair would lead his party into the next election.

The chancellor said the question on whether Blair should go into the next election as prime minister was "a matter for him".

"Tony Blair has been a great prime minister for Britain and I think he has been a great leader of the Labour Party as well," he added.

Number 10 denied the chancellor's comments had been an attempt to undermine the prime minister.

"We saw that interview as being very supportive and continue to see that interview as being very supportive," it said.

But the move came as a minister suggested Brown was not doing enough in private to persuade his supporters to back the government.

Housing minister Lord Rooker said the chancellor should come down hard on those attempting to defeat the government.

"We all know there are a lot of other agendas at work here and the only way this matter can be put to bed is for any of the would-be successors to the prime minister, in or out of the Cabinet, to make their position clear," he said.

"They need to say that anyone going into the Conservative lobby on Tuesday night will never be given a job in a government led by them."

Speaking on Monday, however, the chancellor repeated his support for the policy.

"I want us to be the best educated, best trained workforce, and tomorrow's much-needed reform of university finance - which I urge all MPs and all Labour MPs to support - is another vital step towards that goal," he said.

"Our reforms extend opportunity, they equip young people with the skills to meet the demands of the 21st century, they deserve the support of all who share our goal of securing for Britain the world-class universities now and in the future that this economy needs."