Details of the ¡°core and margin¡± scheme were expected to be made clear in the government¡¯s annual grant letter to the ÖйúAƬ Funding Council for England in January.

But there has been no news on the future of the policy, which for 2012-13 stripped universities of a portion of their non-AAB student places, forming a pool of 20,000 places allocated to universities charging ?7,500 or less and to further education colleges.

The continued uncertainty over the core and margin numbers for 2013-14 has raised fears that the pot of places for low-cost providers could be increased from 20,000, at the expense of newer universities charging more than ?7,500 but without large proportions of AAB students.

Michael Driscoll, interim chairman of the Million+ group of post-1992 institutions and vice-chancellor of Middlesex University, said: ¡°The government should abandon any idea that an extension of the market in student numbers would be good for students.

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¡°In fact exactly the opposite is the case.

¡°To extend the market in 2013-14 will only limit student choice bearing in mind that universities which are tried and tested providers would lose even more student places than this year.

¡°Ministers have had months to decide whether to extend the market but have singularly failed to make any decision.¡±

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Vince Cable, the business secretary, has attributed the delay to universities' ¡°resistance¡± to the core and margin system, saying they felt ¡°destabilised¡± by competition from further education colleges.

However, Sir Alan Langlands, chief executive of the ÖйúAƬ Funding Council for England, has said there are worries within government about ¡°financial volatility¡± from extending the scheme.

Professor Driscoll added: ¡°Many university boards and governors have now agreed fee levels for 2013-14 so that prospectuses are ready for students in the summer term.

¡°Ministers should now put their plans to expand the market on hold and avoid a repeat of last year¡¯s debacle when some universities had to amend fees.

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¡°If the government really does believe in student choice they should allow students to get on with it without imposing further central constraints on universities in terms of fees or numbers.¡±