Blair: Believes he can win vote

At his monthly media conference the prime minister said MPs would vote by the end of January on a policy which he said put his authority on the line.

More than 140 Labour MPs have criticised plans to allow universities to charge students for their tuition.

"There is nothing in the reforms to put people off university... there will be absolutely no retreat," Mr Blair said.

Defeat fears

The government wants to allow universities to be able to charge up to �3,000 per person per year, to be repaid after graduation rather than upfront.

MPs had been expected to vote on the plans before Christmas but the switch to January comes amid reports that Labour's business managers warned Mr Blair the plans faced defeat.

The prime minister insisted that the reforms were necessary to maintain the quality of British universities although he acknowledged he faced a "tough vote".

Students could be charged up to �3,000 a year for tuition

Asked if he would resign if he lost the vote, he said: "Of course my authority is on the line - it always is with issues like this."

BBC Political Editor Andrew Marr said it would be a "devastating blow" if Mr Blair's opponents won the day.

"It is conceivable that if he took this bill to the House of Commons, made all the arguments that he made so forcibly this morning and lost that, it is such an important part of his reform project that his premiership would be gutted," Mr Marr said.

'Triple lock'

Mr Blair argued at his media conference that the plans were socially just - and would end the situation where non-graduates help foot the bill for students who end up earning more because of going to university.

"University education will be free at the point of study and fair at the point of repayment, linked to people's ability to pay," he said.

Mr Blair explained that his "triple lock for fairness" were the fact up-front fees were being scrapped, the fact that capped variable fees would ensure value for money and thirdly, that repayments only began after graduates were earning �15,000.

Asked whether he expected to win over Labour opponents, he said: "There will be absolutely no retreat from it.

"It is essential to keep up the quality of what our universities offer and it is therefore essential for the future of the British economy in which our universities will play a major part."

Later on Tuesday, Chancellor Gordon Brown gave his public backing to getting students to pay more after graduation, without mentioning Mr Blair's preferred option of variable fees.

"That is why, as Tony Blair has said today, it is essential that our reforms proceed through the House of Commons," he said.

Tweaking

Ministers say they are willing to tweak the plans but are sticking by the most contentious idea - allowing different universities to charge different amounts.

One concession reportedly being considered is raising the salary level that triggers the start of fee repayments from �15,000 to �20,000.

But the rebels say only "tinkering" with the proposals will not persuade them to drop their opposition.

Former Labour chief whip Nick Brown, who is considering rebelling against his party for the first time in 20 years, welcomed news of the delay.

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"I hope the delay will be used to consider alternatives and in particular to consider the views of many backbench Labour members of Parliament," he told BBC News.

He said that social justice did not come from burdening the children from families with "ordinary means" with large amounts of debt nor did it come from "allowing the most privileged higher education institutions to increase their fees and just take in rich people".

Professor Ivor Crewe, president of Universities UK and vice chancellor of Essex University, told BBC Radio 4's Today programme that it would be a disaster if the plans failed to become law.

"We are about to submit to the government under the spending review for 2004 a bill for something like �8bn - that is the shortfall in funding for universities at the moment," he said.

"That is what is needed to shore up a crumbling infrastructure and to prevent a brain drain."

Mr Clarke will continue his charm offensive this week as he prepares to lead an education debate in the Commons on Wednesday.