Dr Ron McLone, convener of the Joint Council for General Qualifications, sparked controversy this week. He said rules allowing students to apply for "special consideration" if their examinations were disrupted by bereavement, illness or other serious upsets were being used as cover for an increasing number of bizarre applications.
Last year's excuses, he said, included a student "suffering from intermittent bouts of lethargy" and a candidate who was frightened by a spider in her exam hall.
Another school forwarded an appeal from a pupil upset by the demise of a pet hamster the day before the exam, even enclosing the vet's death certificate. Excuses that students "got up late" or "missed the bus" were common.
Dr McLone, who is head of the Oxford and Cambridge exam board, said: "All boards have seen an increase in applications for special consideration and we have detected a reluctance in some places to be as rigorous as they might be in sifting these appeals."
But other exam boards were reluctant to associate themselves with Dr McLone's comments.
Brian Evans, exam officer at the Welsh Joint Education Committee, said there was no evidence that the appeals process was being misused.
"In the vast majority of instances, the heads screen the applications very carefully," he said.
George Turnbull, spokesman for the Associated Examining Board, said: "There isn't any evidence to suggest this is happening. We have not seen any increase in requests with this board."
There were 250 allegations about cheating during last year's national curriculum tests, according to the Qualifications and Curriculum Authority. But it took action in only three cases.