The Conservatives are unlikely to have lost much sleep over the recent student protests. As the old cry of "Tory scum!" reverberates around London, they conclude that they must be doing something right. But for the Lib Dems, hitherto the party of choice for students on Iraq, civil liberties and free education, the protests are a new and disconcerting experience.

In a sign of his unease, Nick Clegg has written to the NUS president, Aaron Porter, attempting to explain his party's Damascene conversion to university tuition fees. He begins by correctly pointing out that the NUS's "Right to Recall" campaign falsely assumes that the Lib Dems pledged to use the procedure against those MPs who break their promises, not just those who break the rules.

Clegg notes: ". . . my proposal was for it to apply to MPs who were found guilty of serious wrongdoing by the parliamentary authorities. My intention has always been that it should be for people found to be breaching parliamentary rules; the example I often used was that of Derek Conway."

But he is on less sure ground when, in effect, he accuses the protesters of putting poor people off higher education. He writes:

However, I also believe that all of us involved in this debate have a greater responsibility to ensure that we do not let our genuinely held disagreements over policy mean that we sabotage an aim that we all share – to encourage people from poorer backgrounds to go to university. Like me I am sure you have regularly spoken to people who believe that the new proposals will mean them having to pay before they go to university or say that they cannot afford the fees. As you know, there is no upfront charge and the repayments only apply to graduates who earn over £21,000. If the proposals are passed by parliament I believe it is crucial that all of us are able to ensure that people know the true picture.

Clegg is unable to provide any evidence for his claim that the NUS has obscured the "true picture" and his suggestion that the union has misled poorer pupils is likely to be met with contempt. Worst of all, the argument that ever-higher fees will deter students from poorer backgrounds was one made by the Lib Dem leader for many years. Were it not for the coalition, it is one that he would undoubtedly still be making.

It is Clegg, not the NUS, who has all the explaining to do.