Edexcel has come in for considerable criticism following the revelation that its Decision Mathematics (D1) paper last Friday contained a flawed question.

Diagrams on the question paper and the answer sheet had different figures on them, confusing many candidates.

But the board's qualifications director, Paul Sokoloff, said on Wednesday that almost all the 2,500 papers had been marked and two thirds of the students had got that question right.

"What we are now doing is looking at the remaining students who were confused by the error on the question paper and who wasted time and perhaps effort and mental energy trying to solve the parts that didn't work," he said.

Other problems

Mr Sokoloff told BBC Radio 4's Today programme that the board had had a "less than perfect record" over the last year and was "very embarrassed" about its mistakes.

But anecdotal evidence of its incompetence "isn't always real", he added.

Coursework done by 20 performing arts students at North Devon College, reported on Tuesday to have been lost by the exam board, turned up in a college store room.

But other problems have emerged - for example with pages missing from a "key skills" exam on Tuesday.