Gillian Shephard, the Education and Employment Secretary, has acted on advice from both its curriculum advisers and the Office for Standards in Education in attempting to check whether the currency of exam grades is being eroded.

In announcing the study, Mrs Shephard stressed there is no evidence of any decline in standards and, with reference to A-levels, no reason to show any huge concern.

She said: “I believe, given the enormous amount of change there has been since 1988, we can see steady and encouraging progress as demonstrated by the results (at A-level and GCSE). There is, however, no room for any kind of complacency. ”

Before this year’s exams, Chris Woodhead, HM Chief Inspector of Schools, had told MPs on the Commons education select committee that an inquiry would be one way of dealing with public concern about exam standards.

The latest results sparked a further public debate on whether grade inflation had produced more passes, and a slight increase in the proportion of candidates achieving higher grades.

Scrutiny of GCSE results by the School Curriculum and Assessment Authority last year revealed that since the mid-80s the proportion achieving higher grades had been increasing at a faster rate than at A-level. This year’s results showed a marginal decrease in the proportion of candidates achieving higher grades in English and maths.

The new study will track the grading of A-level and GCSE papers in English, maths and science over 20 years. Mrs Shephard dismissed a suggestion that a lack of scripts going back that many years would pose a problem. “There are different ways of looking at standards,” she said.

Mr Woodhead said the purpose of the study was to look at what has happened over 20 years in order to lay speculation to rest.

“We have at this stage no preconceptions about outcomes, but believe we must respond to the public and professional concern that has been expressed over recent years,” he said.

As well as setting up the study, Mrs Shephard attempted to allay a welter of concern about standards. She has asked the Higher Education Quality Council for their comments about the suitability of students accepted for foundation courses in universities, following revelations that places are being offered in the new universities to pupils who have failed A-levels.

She said: “On the face of it, students with no A-level passes do not seem to me to have the right kind of intellectual capability to take a degree. I am aware it needs to be looked at.”

However, she added, she favoured foundation courses that enabled students with inappropriate A-levels to do conversion courses.

The other area being reviewed is vocational qualifications. Mrs Shephard said she was concerned about non-completion rates on courses. She said standards were being monitored by the Department for Education and Employment and the National Council for Vocational Qualifications.

The certification of Advanced General National Vocational Qualifications has come under fire following the revelation that up to a third of students may be still waiting for their awards because of the amount of paperwork required for the assessment. The Universities and Colleges Admissions Service wants to see a review of the certification process. This year, 60,000 students have completed courses, but the NCVQ and the Joint Council of National Vocational Awarding Bodies expect an increase when certification is complete.

* The shortage of maths teachers will become a more acute problem if core skills in numeracy, information technology and communications become mandatory for all post-16 students, the Joint Mathematical Council warned this week. They want more done to attract more students into maths courses at university, and new, and more mature, graduates into teaching, writes Diane Hofkins.

They welcome the proposal that all students should be able to study maths, but in a letter to Sir Ron Dearing in response to his review of 16-19 qualifications, they say more development work is needed before core skills for all can be implemented.

The JMC, an umbrella group of academic and professional societies, is also concerned that under the GNVQ there is little encouragement for good students to extend their mathematics, since the 45 per cent of students who have a GCSE grade C or higher in maths are seen to have fulfilled the core skills requirement.

“We would like everybody to get to the highest level they can,” said Margaret Brown, chair of the JMC and professor at King’s College London. Universities want to know how well students have done in maths, so the system of students simply being certificated in the core skills may be inadequate.

Pointing to forecast shortages in maths teachers, they say: “Even where the supply is sufficient, the quality is insufficiently high. This means in the long term both attracting more students into studying mathematics at university, and attracting new and more mature graduates into teaching. ”