Business Secretary Vince Cable has told the BBC he may abstain in the vote on university tuition fees.
Mr Cable, a senior Lib Dem whose party had opposed raising tuition fees before the election, is now the minister responsible for universities.
He told BBC Radio 5 live his "personal instinct" was to back the rise but he was "willing to go along with my colleagues" if they chose to abstain.
Labour called his comments "extraordinary and appalling".
A vote is due next month on plans to allow English universities to charge £6,000, almost double the current £3,290 cap, and up to £9,000 under certain conditions - something that has prompted angry protests by students.
Meanwhile Welsh universities are also set to raise tuition fees to the same amount - but the Welsh Assembly has said it will meet the cost of extra fees for Welsh students studying at any UK university.
The coalition deal allowed for Lib Dems - who during the election campaign pledged to oppose any rise in tuition fees - to abstain in any vote on an increase in fees.
Mr Cable told the Victoria Derbyshire programme: "My own personal instinct, partly because I'm the secretary of state responsible for universities and partly because I think the policy is right, my own instincts are very much to vote for it but we want to vote as a group."
He said discussions were continuing about how that would happen and he was talking to Lib Dem MPs individually about the policy, which he said was more "progressive" than the one that had been inherited from the previous government.
He acknowledged that the issue had meant his party was "going through a difficult period" adding: "We want to support each other, we try to agree these things as a group as other parties do.
"But as I say my position is somewhat different but I'm willing to go along with my colleagues."
Mr Cable said the plans were "more progressive" than those the government had inherited: "First of all nobody will pay upfront fees, large numbers of part timers, 40% of students at the moment, do pay up front fees. They won't have to in future.
"25% of all graduates will pay less than they do at the moment because it's a progressive scheme and actually 85% of students will have more help when they go to university with the grant and loan scheme.
"In many ways it is a very progressive arrangement and I think that when my colleagues and indeed critics of the scheme really look at it, they will take a different view."
However, research by the million+ and London Economics think tanks, published on Tuesday, suggests 60% of students will be worse off under the plans by an average of £5,000.
Asked about Mr Cable's comments, the prime minister's spokesman pointed out that the business secretary had pointed out that his personal instinct was to vote for the proposals.
He added: "The prime minister is entirely happy that people abide by the provisions in the coalition agreement."
Shadow business secretary John Denham told the BBC: "Here you have a cabinet minister who has personally designed the system that cuts English university tuition funding by 80 percent and makes English students and graduates pay the highest tuition fees of any public university system in the world now saying personally I might well not vote for it - that is absolutely appalling and outrageous."
And SNP home affairs spokesman Pete Wishart said: "His debut on Come Dancing is not till Christmas, but Vince Cable is doing the twist already over tuition fees. As minister with responsibility for universities it is just not tenable for him to abstain in a vote on tuition fees."
In the Commons his party leader, and Deputy Prime Minister, Nick Clegg was challenged about whether he would vote for, or abstain on tuition fees by Labour deputy leader Harriet Harman.
She said Labour would vote against the plans, adding: "If he abstains, it's a cop out. If he votes for it, it's a sell out. Which is it?"
Mr Clegg, who faced numerous questions on the issue of tuition funding from Labour MPs during the session, did not say how he would vote but accused Labour of having no policy on the issue.
During a later debate on the proposals, Mr Denham said the coalition's proposals would see the end of public funding for "most university degrees".
Given the severe financial constraints facing the government, Mr Cable said there was "no alternative" to asking graduates to contribute to the cost of their education or risk "starving" universities of funds.
But Lib Dem MP John Leech said he would vote against any rise in tuition fees, saying it would discourage some students from going to university.
"Call me old-fashioned but I actually support a free education," he said.