The rules? BBC gets starter for 10

The BBC was today under increasing pressure to clarify University Challenge rules after it emerged that four out of the last nine winning teams should have been disqualified.

It comes after this year's winning team, Oxford's Corpus Christi, was stripped of its title because team member Sam Kay had already graduated when the final shows were recorded and was no longer a student.

But it has now emerged that three other teams which have won the televised competition since 2001, including one London university, have fielded ineligible players in the final.

Charles Markland, 23, revealed he transferred from Christ Church to Balliol College Oxford halfway through last year's competition. The Christ Church team went on to win the contest.

Mr Markland claimed his team captain told a researcher on University Challenge about the possible change and was told it was not a problem.

He said: "At the initial auditions in May 2007, my team captain informed the television researcher in charge of conducting the written entry test for teams that I might be at a different college before the series had concluded filming. He was told that this was not a problem, nor a barrier to entry for our team.

"Our captain contacted a researcher again by telephone prior to the filming of the quarter finals to explain that I was no longer at the same college. He was told that for continuity purposes, Granada wished us to field the same team regardless, and that my move was not a problem."

Siegfried Hodgson, a member of the Imperial College team that won in 2001, has admitted that half his team were ineligible. The 29-year-old claimed two members of his team were on one-year masters courses and had therefore graduated by the time the final was filmed.

Mr Hodgson said: "We were completely upfront about this with the production team and there was never any suggestion we broke any rules."

The captain of the 2004 winning team from Magdalen College Oxford, Freya McClements, also left her college by the time the final was filmed and was registered as a student at the University of Dublin when she led her team to victory over Gonville and Caius College Cambridge.

A BBC spokesman said: "The BBC had not been told about these alleged transgressions at the time and so was not in a position to do anything about them."