Labour rebels are expected to use a Liberal Democrat debate on university top-up fees to inflict further damage on the prime minister.

A total of 173 Labour MPs have signed early day motions opposing the fees, which critics argue will create a "two-tier" university system and prevent poor students going to the best institutions.

"There's an awful lot of opposition to this [issue] on our side, and I would imagine an awful lot of abstentions," said Dr Ian Gibson, MP for Norwich North and a rebel leader.

"I'm not sure how many people will hold their nerve, but this is a real opportunity to make a principled stand."

Meanwhile, more than one in five British universities is in financial trouble and risks being closed or taken over, according to a new audit by HSBC bank.

Although the report does not identify the vulnerable institutions, their conclusions will be used by ministers as justification for the introduction of the controversial fees.