• Lady Williams describes plan as 'a very fair policy'
• Liberal Democrat leader tries to unite party before vote
• Thinktank warns new scholarship fund may prove inadequate
A senior Liberal Democrat peer today threw her weight behind Nick Clegg as she urged party colleagues in the Commons to back the tuition fees package.
Speaking ahead of a meeting this evening at which the Lib Dem deputy prime minister will seek to corral colleagues behind the proposals, Lady Williams said Lib Dems "have to vote for this policy", though she conceded it had been a "mistake" for Lib Dem MPs, including Clegg, to have signed a pre-election pledge to oppose any increase in fees.
Clegg sought to press home the case for higher tuition fees today by insisting the plans will make universities "more effective engines of social mobility" and that the policy will "stand the test of time", as he embarked on a last-ditch offensive to dispel "unhelpful myths", notably that the new funding system will worsen social mobility.
Williams backed his corner this lunchtime by insisting that the fees package was "very fair indeed to those at the bottom of the income scale", because it provided for scholarships of up to two years' tuition for young people from disadvantaged backgrounds and delayed repayment of fees until graduates are earning £21,000.
"It has been carefully tailored to assist those at the bottom of the heap and I think the student protesters have not sufficiently recognised the efforts that have been made to try to help the least well-off students," Williams told BBC Radio 4's World At One.
"I think we have to vote for this policy. It is a very fair policy. It is a hard policy, but we know we are going to have many hard policies to come."
Clegg is under pressure to persuade his MPs to remain united at tonight's meeting, though he faces an uphill task after it emerged that two junior ministers — the transport minister, Norman Baker, and the equalities minister, Lynne Featherstone — are considering whether to abstain or vote against, a move that might require them to resign from the government.
The coalition agreement allows Lib Dem MPs to abstain on tuition fees, but it is not clear how this applies to ministers. At least 13 backbenchers, including former party leaders Charles Kennedy and Sir Menzies Campbell, plan to vote against, with Vince Cable, the business secretary, leading a group planning to vote for the measures.
The proposals have triggered a grassroots revolt, it emerged last night, as members of the party's policy committee demanded powers to rein in ministerial independence from Lib Dem policy. Separately, proposals were being put forward by some activists to make it easier for local parties to deselect Lib Dem MPs.
To add to Clegg's woes, a universities thinktank has challenged claims by ministers that proposed scholarships for the poorest students will boost social mobility.
Writing in today's Financial Times , Clegg acknowledged the row raging over the fees policy, but insisted this could be a positive sign in the long-term. "The government's plans will fix higher education funding, with a fairer repayment system and more financial security for universities," wrote Clegg. "History teaches that the best and longest-lasting reforms are controversial when introduced. Right now, our plans are causing plenty of controversy. But I am confident that they will stand the test of time."
Clegg said the public had to face the "uncomfortable truth" that the growth in university student numbers over recent years "has done little or nothing to boost social mobility". Improving people's life chances was the coalition government's "overriding social policy goal", he added.
Clegg cited the new £150m national scholarship fund as a measure which he said would help the poorest applicants, and claimed that tougher access requirements for institutions charging up to the £9,000 fees cap would open the doors of the best universities to a wider mix.
The claims were put in doubt by a university thinktank, which warned today that the scholarship funding pot might not be enough to pay the fees of students who would qualify.
The scheme is intended to fund a year's free tuition for students from the poorest backgrounds — those who received free meals when they were at school. Universities charging more than £6,000 in fees would be required to give a second year free to poorer students.
The thinktank Million+ calculated the scholarship scheme could fund 8,333 students at £6,000 a year, or 6,944 at £7,200 a year. If fees were £9,000 a year, it would fund 5,555. Yet figures show that of the students graduating last year, there were 10,670 who had been in receipt of free school meals.
The thinktank added that proposals requiring universities to match-fund a year's free tuition would have damaging consequences for universities that contribute most to social mobility by admitting more students from disadvantaged backgrounds.
In a letter to the universities minister, David Willetts, Pam Tatlow, chief executive of Million+, said students who had received free school meals were not evenly distributed between universities. Tatlow added: "A requirement to fund free tuition is more likely to increase rather than decrease fees in those universities with more free school meal students. Nick Clegg has also implied that universities which provide two years' free tuition will be compensated by the government.
"Only those institutions with very few free school meal students and big endowment funds are likely to be able to afford to do this. This would immediately disadvantage free school meal students studying at universities with more socially inclusive profiles," warned Tatlow.
Clegg's claim that social mobility will be improved as a result of the measures has also been challenged by David Davis, the Conservative MP and rightwing standard-bearer, who has announced that he will rebel in the key Commons vote on Thursday because of the damage he believes the fees rise will inflict on social mobility, sparking fears that a few other rightwing Tories might also break ranks. However, a coalition majority in Thursday's Commons vote is not believed to be under threat.