Young people from poor backgrounds face a "postcode lottery" over information and advice about university following the decision to axe a national access scheme.
The warning was made this week after David Willetts, the universities and science minister, revealed that funding for Aimhigher will cease next year.
The government wants to establish a new framework for widening participation that places more responsibility on universities.
But experts said institutions would not be able to give as full and impartial a picture about higher education, and warned that young people in regions without universities could be left out altogether.
Jo Wiggans, director of Aimhigher Greater Manchester, said information, advice and guidance would be even more important if tuition fees increase. Aimhigher will be wound up next summer, but the choices faced by applicants in 2011-12 will be "harder and more complicated than ever before", she said.
Ian Tunbridge - deputy vice-chancellor of Thames Valley University and chairman of the Aimhigher West, Central and North London partnership - said the programme had provided school pupils with impartial advice about the benefits of going to university.
By contrast, he said: "I wouldn't expect to be able to work with a network of local schools around here and give a very strong picture on what Oxbridge entry is about.
"Equally, I wouldn't expect the universities of Oxford or Leeds to be able to talk about progression routes for advanced apprentices moving into part-time and work-based study."
The limits of local knowledge
Saying that it appeared that the government had given "no thought" to the implications of its decision, he warned that a "postcode lottery" could emerge in the quality of advice.
Aimhigher was set up to encourage young people from disadvantaged backgrounds to aspire to university study. It runs via 42 partnerships across England, which work with about 2,700 schools, offering activities such as taster sessions.
David Lammy, Labour MP for Tottenham and the former higher education minister, said the initiative carried out "a staggering amount" of work to tackle the perception that university was only for some.
He said he was "very concerned" that MPs may be asked to vote on the future level of tuition fees without proper scrutiny of the legislation and the policy to support widening participation. "Is this something that, in the end, will be down to good faith?" he asked. "I don't think that is acceptable."
Lee Elliot Major, director of research and policy at the Sutton Trust education charity, said Aimhigher had achieved "a huge amount" but was vulnerable because it lacked "robust evidence" of its impact.
However, Graeme Atherton, executive director of Aimhigher West, Central and North London, said there was a "vast array" of evidence but the government had done a poor job of collecting it.
Research by Aimhigher found that students who participated in more than seven of its activities were 50 per cent more likely to do extra work to boost their grades, he said.
Aimhigher received £250 million between 2008 and 2011.