Education Secretary Michael Gove's plans to separate AS-levels from A-levels risks damaging a decade's worth of work to encourage more disadvantaged teenagers to study at Cambridge University, the prestigious institution has warned.
The proposed major overhaul has been criticised as teenagers taking A-levels will no longer sit exams after one year.
Cambridge University said knowing the results of AS-levels was crucial in increasing the number of graduates from state schools. A statement released by the institution read: "The University of Cambridge opposes the deletion of AS examinations at the end of Year 12. This change is unnecessary and, if implemented, will jeopardise over a decade's progress towards fairer access to the University of Cambridge."
It said AS-level results were the "most reliable indicator" of an applicant's potential to thrive at Cambridge, and had enabled it to achieve the highest levels of undergraduates from state schools in more than 30 years.
The statement added: "AS results show an applicant's most recent academic achievement and demonstrate progress since GCSE in a transparent and objective way. Neither GCSEs, admissions tests nor school predictions come close to matching the effectiveness of AS in enabling the proper and full assessment of applications."
But Mr Gove said he was worried there was "too much assessment and too little learning". He told the education select committee: "It seemed to me that one of the most effective ways we could encourage the sort of deep thinking that we want to have in people, not just who are going on to university but who are going to be entering an increasingly testing and sophisticated world of work, was to move towards a linear A-level.
"But there are certain gains, of course, in the flexibility which the AS-level has given so we didn't want to completely abolish that. We thought the best way forward was a standalone qualification."
He said the future was "open to debate", including the possibility of pupils taking AS-levels in "balancing subjects" such as English and maths alongside A-levels.
The new A-levels will be taught from September 2015, which is the same time as GCSEs are set to be replaced with new English Baccalaureate Certificates (EBCs).
Christine Blower, general secretary of the National Union of Teachers, said: "2015 looks set to be the year when everything changes in schools and for young people with both GCSEs and A-levels being replaced or altered. This is an unmanageable level of change which could lead to a collapse of the system."