The £56 million given to universities so far to make their campuses accessible to disabled students is not enough to pay for the work needed at Cambridge University alone.
Vice-chancellors have called on ministers to deliver more funds urgently.
Cambridge could need up to £70 million to refurbish its buildings to ensure they comply with the Disability Discrimination Act. The figure is extrapolated from an audit of the central university's 160 buildings - representing half its estate - which identified £33.4 million of work required.
Disability officer Judith Jesky said this week that Cambridge had received just £760,000 from the Higher Education Funding Council for England - part of a £56 million package for 2002-04 for the whole sector.
"We have identified five priority areas for the £760,000, like the university library and buildings that are used most," Ms Jesky said. "But the money doesn't come anywhere near the £33 million we need to make the whole central university estate accessible."
The university - facing a £20 million deficit within three years - was unlikely to find the money from its own resources, she warned. "We have to look to government to find a way."
Oxford University said it needed to spend £6.25 million to get its central buildings - excluding the colleges - compliant. It has so far received £795,000 from Hefce.
All universities must have fully accessible buildings, fitted with features such as wheelchair ramps, lifts, special lighting, signs and hearing loops by September 2005 under a recent extension to the DDA.
Baroness Warwick, chief executive of Universities UK, said: "Universities are working hard to improve access for students with disabilities and to ensure that they comply with new legislation. Additional funding is vital to secure further improvements.
"UUK has therefore lobbied government for additional resources. Our spending review submission outlines the additional funding needs for higher education to cover the cost of complying with new legislation, both in terms of staff development and the teaching infrastructure."
It is unclear how much it will cost the higher education sector to update its buildings specifically for disability access, but UUK has demanded an additional £2.65 billion for general building improvements.
Barbara Waters, chief executive of Skill, the pressure group for the disabled, said: "Institutions should be planning and budgeting for these costs, and this will involve prioritisation - for example, ensuring the library buildings are accessible is likely to be more important for disabled students than access to the vice-chancellor's office."