Teacher unions today welcomed Education Secretary Estelle Morris's decision to hold an independent inquiry into the A-Level grades row.

She faced calls from classroom teachers to reduce the number of exams in the wake of the affair from those who believe the system is under too much pressure because children take exams at age 16, 17 and 18.

Headteachers said it was necessary to wait for ex-chief schools inspector Mike Tomlinson to complete his investigation into how grade boundaries were set before calling for a re-grade of all this year's A-level entries.

David Dunn, headteacher of independent Yarm School at Teesside: "I welcome the inquiry. I'm quite confident that it is going to find that these papers have been manipulated, what we may never know is who gave the instructions. "The whole thing stinks of political manipulation."

In the meantime, they directed their fire at exams watchdog the Qualifications and Curriculum Authority, which they said had left teachers disillusioned and confused about A-level standards.

John Dunford, general secretary of the Secondary Heads Association, said: ''I think we can probably reserve judgment on that for a week.

''The results of the immediate inquiry will then I think demonstrate whether that total re-mark is needed.''

The exam boards should have made the grade boundaries clear to schools months before the exams, not after, he went on.

''It has left some very experienced teachers feeling disillusioned about A-levels.

''Of all the many things that have been brought into question in education in recent years, that is the most damaging to question A-level standards.

''Never have such fundamental questions been raised as has happened this year.'' He blamed a ''major failure of communication between the Qualifications and Curriculum Authority and schools over the last year for the fact that many teachers were confused about what standard A-Levels were now pitched at.

''Whatever else the inquiry finds, I'm sure it will reflect on that failure.''

David Hart, general secretary of the National Association of Head Teachers, said: ''The Secretary of State's decision is a victory for commonsense and recognition that the position of the QCA was totally and utterly untenable.

''It also reflects the pressure applied by headteachers who have been able to secure belated justice for this year's students and the promise of reforms for the future, which will prevent a repetition of this year's fiasco.''