The Liberal Democrats have called for A-level league tables to be abandoned after the findings of Roger Porkess, project leader for Maths in Education and Industry.
Mr Porkess, who writes an independent A-level syllabus for OCR, the board at the centre of the exam furore, claims the Tomlinson Inquiry was too restricted.
As The TES revealed, the regrading exercise at OCR only reviewed papers where there had been extreme jumps in the grade thresholds of six marks or more. As a result fewer than 2,000 students received a subject upgrade.
No estimates were made about how many students would have been upgraded if the inquiry had looked at papers where the boundary was suddenly moved by five or four marks.
Mr Porkess said: "The application of the (six-mark) cut-off will inevitably have left some candidates with a lower A-level grade than would have been the case if all thresholds had been restored to those (originally) set by the awarding committees." He claims 15 per cent of candidates who took papers where the grade boundary was raised by five marks would have been upgraded.
He also claims that, where regrading did occur, the grades were not restored to those set by the awarding committees.
Thousands of teachers and pupils feel let down by the regrading process. OCR officials have faced angry teachers at feedback sessions.
One teacher said: "Exam board staff are now able to hide behind Tomlinson... there were no answers to my fundamental questions."
Phil Willis, Liberal Democrat education spokesman, said Mike Tomlinson had admitted to him at a meeting that he could not give an assurance that every student had received the grade they deserved this year.
Mr Willis said: "This was not a storm in a tea cup, it was a major scandal... Trust cannot be rebuilt until there is an admission that all is not well with this year's results."