Oxford University was unsparing in its criticism of David Cameron after the Prime Minister drew attention to its shameful record on admitting black students. But rather than launching a counteroffensive, Mr Cameron's alma mater should have used this as an opportunity for introspection. Mr Cameron may have been wrong to claim that Oxford accepted only one black student in 2009 - he should have said it accepted only one black British Caribbean student - but this fact is scarcely less terrible.

The figures in question were revealed last year as a result of Freedom of Information requests by the tenacious Labour MP David Lammy. They showed that 21 Oxbridge colleges made no offers to black candidates in 2009 and that one Oxford college, Merton, had not admitted a single black student for five years. Yet 292 black students achieved three A grades at A-level in 2009 and 475 applied to Oxbridge. As Mr Lammy concluded: "Applications are being made but places are not being awarded."

Oxford's performance compares poorly to that of the American Ivy League universities, which use extensive outreach programmes to attract bright students from ethnic minorities. Harvard, which recently admitted record numbers of African-American and Latino students, writes to every high-achieving minority pupil in the US. Yale employs access officers in each of the 50 states. By contrast, in a bizarre use of resources, 21 per cent of Oxford's outreach events are held at private schools, including nine "access events" at Eton and 12 at Marlborough College. The university's record on admitting students from the poorest homes is little better. As Nick Clegg notes, only 40 students who received free school meals were accepted by Oxford and Cambridge last year.

Mr Cameron and Mr Clegg, who have made increasing social mobility one of the defining aims of the coalition, are rightly outraged by these figures, but their decision to triple tuition fees to a maximum of £9,000 a year risks making the situation worse. When the fees legislation was passed by a majority of just 21 votes in December, ministers assured the public that universities would charge £9,000 in "exceptional circumstances" only. But of the 47 institutions that have announced plans, 35 intend to charge the maximum fee, including several former polytechnics. As a result, the reforms, modelled on an average fee of just £7,500, face a funding gap of nearly £1bn. New figures from the Commons library show that if the average fee is £8,600 (it is currently £8,709), the state will have to spend £960m more on subsidised loans over the next four years. The reckless decision to cut the teaching budget by 80 per cent, combined with universities' desire to appear reassuringly expensive, made such an outcome predictable.

Those institutions that charge £9,000 will be required to spend £900 of that income on access for poorer students. But the danger is that pupils from the poorest backgrounds will be deterred from applying at all. Mr Cameron's rhetoric must be supported by policy. The decision to raise tuition fees, abolish the Education Maintenance Allowance and cut Sure Start, a service on which black and minority ethnic families are disproportionately reliant, shows that, for now, it is not.