Nick Clegg has spoken of the need for spending cuts
Lib Dem leader Nick Clegg has said the party will keep its pledge to scrap tuition fees despite earlier saying they might not be able to afford it.
Mr Clegg told his party conference tuition fees were "wrong" but "we need to treat people like grown-ups" and scrapping them would cost billions.
But his words sparked anger among some grassroots members who have the final say over what goes in the manifesto.
Now Mr Clegg says he would phase out the fees over six years.
Under the plans, which would not see tuition fees finally scrapped until the Parliament after next, fees would first be scrapped for final-year students, in the financial year 2010-11, at the cost of £511m.
The overall cost of the policy over six years would be £7.5bn.
The party said full costings would be released nearer the election, but funding would come in part from scrapping or scaling back existing government schemes.
In a message to party members, Mr Clegg said the party's Federal Policy Committee, which has the final say over what goes in the manifesto, had "agreed a way to deliver one of our most important policies, the scrapping of unfair tuition fees".
He said: "We've developed a plan to phase out tuition fees over the course of the next six years, to ensure this vital policy is affordable even at this time of economic crisis."
He said the recession had made it "more difficult to find the money to fund our priorities".
"That's why we are right to adapt our plans for big spending commitments and why it is right that our general election manifesto will focus this time on a smaller number of key commitments.
"But our message to students is clear: we remain the only party that believes fees are unfair, and the only party with a plan to get rid of them for good."
At the party conference, when the leadership suggested sticking to their commitment to scrap tuition fees might be too expensive, there was strong public dissent from senior figures, including the former leader Charles Kennedy.
Mr Clegg has been outspoken about the need for spending cuts and to stress the party's economic credibility.
In a speech to the party faithful in September, Mr Clegg said: "I believe tuition fees are wrong. I believe they need to be abolished. I want to do it as soon as possible.
"But we need to treat people like grown-ups, and we need to be realistic.
"Ending tuition fees would cost billions of pounds every year. We need to be certain we can afford it before we make any promises.
"But I can make this pledge: at the next election we will have the best, most progressive package for students of any mainstream party: that is my guarantee to you."