A leading Oxford don has attacked the country's "gold standard" A-level exams, claiming it had been watered down over the past two decades.

Sixth formers' A-Level results in the county showed an overall pass rate of 98 per cent, and results nationally improved for the 25th year running.

But Alan Ryan, Warden of Oxford University's New College, said a generation had been failed by politicians aiming to send 50 per cent of youngsters to university.

Mr Ryan claimed A-Levels had been watered down to give thousands more sixth formers the grades they need for university.

The political philosophy lecturer spoke out on Thursday, the day when sixth formers were set to break A-Level records by passing at least 25 per cent of exams at Grade A - up from 15.7 per cent a decade ago.

He said: "Less than 50 per cent of each age group gets five decent GCSEs, including maths and English.

"We are therefore intending to give degrees to students who cannot get a C at GCSE in maths and English.

"If we are providing remedial secondary education, shouldn't we say so and distinguish it from the sort of degree-level physical chemistry that makes your brain hurt, even after an A in further maths?"

In a devastating attack, Mr Ryan said planned Government reforms, including an A* supergrade, would not be enough.

Instead, he said, a far-reaching overhaul was needed to ensure students displayed in-depth knowledge of a subject rather than simply an ability to match answers to a rigid marks scheme.

Mr Ryan added: "We are always told not to belittle the students on their day of glory - nobody should need to be told that.

"But we should belittle the adults who have spent the past two decades trying to square the circle.

Results across the country were predicted to show a surge in the A-grade pass rate for a 10th successive year, with more than one in 10 students expected to achieve three straight As.

Mr Ryan added: "As to A-Level, the game is clearly up. It can't simultaneously be true that A-Level provides a gold standard and that it needs a wholesale overhaul.

"The main losers are not the universities that can't separate the best students from their competitors. They are the students who could have learnt a lot more and learnt it more interestingly."

Some universities, including Oxford, have used entrance exams to help identify the brightest students from a growing field achieving A grades.

A spokesman for the Department for Children, Schools and Families, said: "Standards are rising because teaching has improved and pupils are studying harder.

"We find it depressing to hear students' achievements decried on a day when they are waiting to find out their results."