The Government was expected to bow to pressure for an independent inquiry into the grading of the newly-designed A-level as it announced that thousands of entries at the centre of the row were to be re-marked.
The inquiry call was backed by the chief executive of OCR, the exam board accused of moving the goalposts to avoid a politically unacceptable rise in top grades.
In a letter to schools, Dr Ron McLone admitted bright pupils had been penalised to "balance" results, but said OCR had followed the rules and done no more than other boards to maintain year-on-year standards. "My job is to be honest and fair to all students and that has been the overall outcome," he said.
The unprecedented shift in grade boundaries this summer has led to inexplicable sets of results with some pupils achieving A grades in exams and very poor grades in coursework.
Some senior examiners complained that OCR had "leaned" on them. One described how he received the grade boundaries "with disbelief" and labelled it "creeping E syndrome".
A student from independent school Dulwich College, south London, who turned down Yale and Oxford to go to Harvard, and who has never received less than a top grade, got a C grade in coursework.
High-performing state schools have also been affected. Pupils at the London Oratory, where Prime Minister Tony Blair's son Euan took the exams this year, have fallen victim to the 11th-hour grade deflation.
Headteacher John McIntosh said: "We have concerns about the results from OCR which are very similar to those from other schools.
"We do not understand why pupils have received some coursework grades. These examples are so stark that something must be amiss. We need to have a very clear explanation."
AS-level results have also been called into question and schools are reporting similar problems with exam boards AQA and Edexcel.
Writing in today's TES, Geoff Lucas, secretary of the Headmasters' and Headmistresses' Conference, calls for an urgent re-appraisal of the system. He says the need to achieve comparability with last year's results took precedence over the need to be fair to this year's candidates.
HMC, the Girls' Schools Association, and the Secondary Heads Association have demanded that original grade boundaries established by awarding committees before subsequent statistical manipulation are restored and all 1.5 million results re-issued.
They dismissed the Government's offer of re-marking disputed scripts and accused the Qualifications and Curriculum Authority of putting pressure on the boards to downgrade. The QCA will report to ministers today, but schools believe the quango is too involved in the exam process to lead an inquiry.
David Hart, the general secretary of the National Association of Head Teachers, said: "What we cannot afford is some sort of whitewash."