Proposals to let universities charge wealthy students much higher tuition fees risk turning the clock back to when "breeding not brains" mattered, ministers were warned today.
Students from the richest families should not be able to "buy" higher education places, the University and College Union (UCU) insisted.
Universities minister David Willetts confirmed that the Government is looking at proposals to increase student numbers by allowing English universities to charge some UK applicants the same fees as those paid by overseas students from outside the EU.
He suggested the move could open the way for charities and other organisations to sponsor students who would otherwise not be able to get places.
However, the proposal risks exposing the Government to charges that it would simply enable the children of the wealthiest parents to buy their way in.
UCU general secretary Sally Hunt said the proposals highlighted the problems with the Government's tuition fees policy, and were particularly embarrassing for the Lib Dems, who campaigned against higher fees in the run up to the general election.
"I am amazed that such plans are under consideration," she said.
"We have seen considerable changes made to Government policy recently and it is clear these plans need an urgent rethink.
"Far from increasing social mobility, it is hard to see how this is anything other than the Government entrenching privilege for the wealthy in response to its failing university fees policy. We risk turning the clock back to a time when breeding rather than brains were required to get on in life.
"The news is particularly embarrassing for the Liberal Democrats as all their MPs pledged to vote, and campaign, against higher fees.
"Increasing fees for wealthy students to ensure them access to our most prestigious universities goes even further than their original breaking of the pledge and sends an extraordinary message to students from less wealthy backgrounds."
Mr Willetts said that if the scheme was adopted, it would have to meet the Government's objectives of improving social mobility, although he offered no suggestion as to how this could be achieved.
Under current Government plans, annual student numbers are capped to keep costs down with English universities allowed to charge UK students a maximum fee of £9,000 from 2012, which graduates do not have to start paying until they are earning £21,000.
However, Mr Willetts suggested universities could increase the numbers of British students by charging some the full annual fees of up to £28,000 a year for the most expensive courses, payable up front, who would not then require the support of the taxpayer.
"People are coming to us with innovative ideas about how you could liberalise the system so it was possible for extra people to get to university," he told the BBC Radio 4 Today programme.
"These are people who we wish to go to university and who sadly are being turned away at the moment just because there aren't enough places.
"We would need to have a set of criteria, if this went ahead, that absolutely passed muster as improving social mobility.
"I start from the view that, by and large, more people going to university is a good thing for social mobility. Anything that we did if this does go forward would have to pass the test of improving social mobility, not reversing it."
Aaron Porter, president of the National Union of Students (NUS), said: "The Government is yet again tossing out a poorly conceived policy idea in an attempt to disguise the chaos it has created in university funding and the shortfall in finances that has created.
"This creates a two-tier system that allows the richest, less able applicants a second bite at the university cherry and denies low- and middle-income students the same opportunity.
"Those students who can afford to pay higher, upfront fees will also avoid the interest rates and lifetime of debt that the rest of their cohort will have to consider when considering university."