The Government’s chief curriculum adviser, by proposing a system of 16-19 alternatives rather than a single route to a qualification, is understood to be trying to sidestep ministerial pressure to maintain the A-level “gold standard”.

Conservative defenders of A-levels would find it difficult to oppose testing possible reforms in the marketplace. Success would then depend on the take-up of the certificate option by schools and colleges and the interest shown by university admissions departments and employers.

Under the national certificate model students would study five subjects in the first sixth-form year, then specialise in order to take two or three A-levels the following year as they do now. The unpopular AS-level would be reformed to become an optional intermediate exam between GCSEs and A-levels, similar to Scottish Highers.

Sir Ron, whose report is due next Easter, is also likely to propose reforming general national vocational qualifications as “applied A-levels”, boosting attempts to create parity of esteem between academic and vocational courses.

At the close of consultation on his qualifications review last month, Sir Ron, chairman of the School Curriculum and Assessment Authority, revealed that he was considering three models, all leading to a national certificate. All allowed a mix of academic and vocational studies, though students would still be free to take the traditional three A-levels.

However, ministers are understood to have subsequently warned Sir Ron against recommending any overarching qualification. Exam boards had already raised concerns about how such a certificate would be organised, who would collate the information, and how the process might be funded.

Professor Alan Smithers, director of the Centre for Education and Employment Research at Manchester University, has proposed reforms similar to those now believed to be favoured by Sir Ron, though he sees no need for any national certificate to overarch the reformed qualifications structure.

He supports a move to convert the AS exam into a “half-way house” to A-levels, claiming the change would “make it possible for more subjects to be studied in the sixth-form years without diluting A-levels as the Government fears”. Over time, Professor Smithers believes, many students might be able to gain five A-levels.

New “applied A-levels”, regulated by SCAA rather than the National Council for Vocational Qualifications, would attract the prestige still denied to GNVQs, he adds. The change would also do away with duplication in subjects such as business and technology, where both GNVQs and A-levels are currently on offer. Appropriate combinations of subjects would emerge across the five AS qualifications, with no need for concern over parity of esteem, Professor Smithers believes.

However, the certificate model, though maintaining A-levels, is still likely to upset traditional Tories. James Pawsey, chairman of the Tory backbench education committee, says moving from three to five subjects in first year of sixth form would water down A-levels.

“I would look on such a model with a jaundiced eye because once A-levels are diluted it will ultimately also raise questions about the quality of degrees, ” he says. “It may be Sir Ron is looking towards a four-year degree.”

The moderate Tory Reform Group, which has supported the abolition of A-levels, backs the call by some school and college organisations for the wholesale dismantling of the current qualifications in favour of a fully unitised system.

Giles Marshall, TRG executive member, condemned any move to the market as an “abdication of responsibility” which would “treat students as guinea pigs”.

SCAA will not comment on the direction of Sir Ron’s thinking, though assistant chief executive Tony Milens acknowledged the reform of AS-levels into a mid-sixth-form exam had been raised in consultation.