A preliminary report into alleged grade-fixing of A-level results in England will be published on Friday.

But as the exams watchdog was putting its final touches to its first report on the crisis, head teachers increased the pressure on it by calling for an investigation into the marking of GCSEs.

In its preliminary report on A-levels, the Qualifications and Curriculum Authority (QCA) is expected to say there was no malpractice or improper intervention in the marking of course work done by one exam board.

The report, on marking by the Oxford and Cambridge and RSA (OCR) exam board, will be given to Education Secretary Estelle Morris.

Ms Morris bowed to pressure for inquiry

Now the National Association of Head Teachers (NAHT) says it is gathering evidence that GCSEs in music, English literature and English language have been affected by "slipshod marking".

The QCA's inquiry was sparked by schools who questioned how students who scored A grades in exams got Ds, Es and even unclassified or fail grades in coursework.

The report comes the day after Ms Morris announced there would be a full independent inquiry into claims that three exam boards fixed grades.

Tory leader Iain Duncan Smith welcomed the move, but insisted those found responsible "should pay with their own future".

He wants the government to extend next week's emergency recall of Parliament to two days, so MPs returning to discuss Iraq can also debate the A-level crisis.

Political interference denied

The exam row, which began as concern over marking by one exam board, has escalated to include allegations that the QCA itself forced exam boards to mark down papers to offset claims exams were getting easier.

The education secretary has insisted there has been no political interference in exam marking.

But head teachers say that since thousands of exam papers are now having to be re-marked, this year's A-level league tables should be scrapped.

Tomlinson inquiry into:

Claims of grade-fixing Role of exams watchdog, QCA Claims of political interference Claims of falling standards in exams

The Secondary Heads Association says tables based on inaccurate grades would be a "nonsense".

General secretary John Dunford said: "It beggars belief that they would be constructed on the basis of inaccurate results."

It is expected that Friday's report by the QCA will dismiss allegations of fixing of coursework marks as a "storm in a teacup" but will admit something untoward happened with about half a percentage of exam scripts this summer.

Teacher training 'inadequate'

It is likely to blame poor support and training offered to teachers by the exam board.

Meanwhile in the independent inquiry, Mike Tomlinson, the former chief inspector of schools in England, will examine the wider claims that exam boards marked down results after pressure from the QCA.

This accusation has been denied by the exams watchdog.

Mr Tomlinson will also investigate persistent claims exams are getting easier.

Take education right out of the political arena

Derek Blyth, UK

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His preliminary findings are expected within a week.

Many pupils have complained to BBC News Online they may have lost out on university places because of unfair marking.

Ms Morris has said if it was proved students missed a university place, they would be offered a place at that institution in the next academic year and the government would try to help universities offer a place for this academic year where possible.