Witney MP David Cameron is calling on the Government to review the A-Level examining system as the pass rate is expected to rise to an all-time high.

Results are out on Thursday, August 18 and are expected to show a rise from 96 per cent to 97 per cent of entries awarded A to E grades.

Earlier this year Ruth Kelly, the Education Secretary, pledged to make A-Levels harder after complaints of falling standards, but a spokesman for the Department for Education and Skills said planned reforms outlined in a White Paper in February, including setting tougher questions, had come too late to affect this year's results.

Shadow education secretary Mr Cameron said: "Students have worked hard and they deserve all the success they get but as more people get A grades in their results, we will have to ensure that A-levels are doing what is necessary, and that is showing the difference between those students who are good and those who are outstanding."

Mr Cameron said there were various ways in which ministers could amend the system but this should be discussed at a later date.

He added: "You could publish marks as well as grades and you could create distinction grades, but that's something for the future."

If there is a rise this year, it will be the 23rd in succession. The proportion of pupils achieving A grades is also expected to rise this year to 23 per cent, compared to 8.6 per cent in 1982.

To distinguish themselves from the mass, many brighter pupils now take six or seven A-Levels.

A Government spokesman said: "A-Levels will stay. They are tried, tested and trusted, but we recognised that we need to increase the stretch and challenge within A-level for our brightest students."

Nick Seaton, chairman of the Campaign for Real Education, said: "These rises every year surely indicate that A-levels must be toughened if they're going to be any use to universities and employers.

"If we are going towards 100 per cent, the exam is no use in measuring standards."

One proposal which could be announced in the Autumn by Ms Kelly is that the brightest A-level candidates should attempt an extra set of harder questions at the end of their exam.

If they pass the optional half-hour extension paper they would get an A grade with distinction or merit and gain an advantage in the race for places at the best universities.