LONDON - Achieving three A grades at A-level will no longer be enough to ensure a place at a top university, academics warned on Wednesday.

From September sixth-formers will begin studying A-level exams which will include a higher grade of A* for those getting marks of 90 percent or above in their papers.

Those applying for Oxford or Cambridge will need a brace of the new top grades to win a place, the 1994 Group of 19 leading universities said in a report.

It said it expected the two elite universities to take a large majority of those awarded three or two A* grades.

Outside Oxbridge, students will need at least two A* grades and standard A grade to be confident of getting a place at their chosen university.

The extra grade is being added to meet complaints from universities that too many pupils gain maximum grades in A-levels, making it hard to select the most able.

But the 1994 Group, which does not include Oxford or Cambridge, said there were concerns among its members that pupils from fee-paying independent schools would dominate the A* grades.

It said this could set back efforts by its member universities, who include Durham, St Andrews and Warwick, to widen the social range of their intake.

The report estimated that just 3,500 out of 660,000 students would be awarded three A*s when they take the first exams in the new A-level courses in 2010.

That compares with the 26,200 students who gained three A grades in A-levels in 2006.

The government said there was no evidence to show that state school pupils would be disadvantaged by the introduction of the new grade.

"It is up to institutions to decide how they balance their assessments of applications with their desire to be fair and to offer places to applicants with the greatest potential, regardless of background," said a spokesman for the Department for Children, Schools & Families.