BELEAGUERED exam board Edexcel was under fire again yesterday as details emerged of another test blunder.

Hundreds of students were thrown by a misprint in their AS-level paper on government and politics.

The exam board said the error was initially spotted by a proof reader and a new paper was sent to the printer. But the old paper was reprinted as well as the corrected version.

Although most schools were told about the error before the exam, some were not informed until half way through the three-hour test.

At Yarm School, near Stockton, which highlighted a printing error in a maths paper set by Edexcel earlier this year, staff were informed in time.

But headteacher David Dunn said: "The exam season has only just begun and I don't think it will be the last error we see."

Pupils were asked to compare and contrast the Liberal Democrat Party's election results in 1997 and 2001, but the results were printed the wrong way round.

A mother of one pupil in Durham, who sat the exam, said they had not been told until half way through.

She said: "Luckily, my child realised that there was a mix-up and that the results were in the wrong place, but a few of the pupils didn't."

An investigation was under way yesterday to determine who was to blame for the error, but it is the latest in a series of controversies surrounding Edexcel.

They include setting an unanswerable maths question and missing pages on a communications exam.