University top-up fees are bound to rise above £3,000 a year if they are approved, say the Conservatives.
Many students oppose fees
Shadow education secretary Tim Yeo told MPs universities would not receive enough money in the first instance and would want to raise more.
He spoke during education questions in the Commons, when ministers faced a barrage of questions about their controversial plans for university funding.
The government is battling to win over backbench rebels.
Mr Yeo said: "Will the government therefore not be announcing quite soon an increase in
"Any assurance you try to give of a verbal nature on this matter is
undermined by the fact that the whole policy represents a breach of the promise
that the government made to electors less than three years ago."
The Education Secretary Charles Clarke told Mr Yeo the £3,000 limit on tuition fees would only be lifted "after very full consideration
and by a vote of every member of this House".
He said it was a "bit rich" of the Conservatives to warn against rising fees.
"Your proposal takes hundreds of millions of pounds out of the universities
and reduces, by hundreds of thousands, the numbers of places available," he said.
MPs are due to debate the government's Higher Education Bill on 27 January.
Labour's David Taylor complained that higher education was being made into a market.
"Isn't it the case that this is not about the small amounts of extra finance
that would be rather slow to come or the expansion of opportunities for working
class students. It's about marketisation."
Higher Education minister Alan Johnson denied this, insisting: "It's about getting rid of upfront fees,
reintroducing a maintenance grant of £1,500 and making it easier for graduates to repay not just any fee but also their loans."