The examination board, Edexcel, which came under fire earlier in the year, is facing fresh criticism over plans to allow trainee teachers to mark some papers this summer.

The board says it has selected 30 student history teachers to mark GCSE history papers as part of an experiment to tackle the annual shortage of examiners.

Edexcel insists the trainees will be closely supervised by senior staff.

This is not something we would encourage because we want the best expertise to be used Maggie Scott Association of Colleges

But the Association of Colleges has condemned the plan, saying markers should have at least two years' teaching experience.

Edexcel was severely criticised in January when it emerged that mistakes had been made in AS level maths and physics papers.

Education Secretary Estelle Morris sent a troubleshooter in to sort out problems at the board and it will remain on probation until after this year's exams.

A spokeswoman said the experiment involved 30 examiners out of 15,000 that would be working for Edexcel this summer.

'Pro-active'

They would only be marking part of students' history GCSE work and would do so under the scrutiny of both senior and chief examiners, she stressed.

"They have more training than new examiners generally have and are well up to date with the curriculum," she added.

"People are well aware that there are shortages of examiners and we are being pro-active in looking at ways of finding people within the education field who may be in a position to examine in the future."

Examiners do not have to be serving teachers - many are retired or work as university lecturers.

But Maggie Scott, curriculum and quality adviser at the AoC said: "This is not something we would encourage because we want the best expertise to be used, people with experience in the classroom but also of assessing and marking.

'Imaginative'

"Up until now there has always been a requirement for markers who are teachers to have had at least two and probably three years' experience and we wouldn't want to see that changed."

A spokesman for exam watchdog the Qualifications and Curriculum Authority said it had been encouraging boards to come up with "imaginative" ways of recruiting more markers.

The students were all postgraduates and would almost have completed their training by the time they started looking at scripts, he added.

Candidates' papers would be checked by at least three different examiners, and the spokesman stressed: "There's no question of diluting quality here."