Recent figures suggest that the number of children doing up to one hour of homework has dropped from 86 per cent (of girls aged 12 and 13) in 1991 and 1997 to 64 per cent last year.

David Regis, the unit’s research manager and a former teacher, said that the findings were unexpected. “Pressure on schools has never been higher, so they are curious findings,” he said.

“We don’t know if they’re being set less or are doing other tasks, such as coursework, which they are not calling homework. Or maybe teachers have decided that the emphasis on the academic curriculum and homework is not doing our children any good at all, and maybe they are right.”

Researchers questioned 448,124 young people between 1983 and last year. In 1991, after the introduction by the Conservatives of the national curriculum, teenage girls and boys were apparently working significantly harder.

Showing a similar trend to that of 1997, 12 to 13-year-old girls were the most studious, with 86 per cent claiming to do an hour’s homework and 72 per cent doing two hours. Last year, however, just 64 per cent studied for up to an hour and 57 per cent for up to two hours.

Boys aged 14-15 have consistently shown the least interest in homework. In 1991 and 1997, almost three quarters were doing up to an hour. That figure has since dropped to about 56 per cent.

Alan Smithers, director of education and employment research at the University of Buckingham, said: “It may not be the same amount, but it could be more quality and relevant homework that fits into the curriculum structure. So it’s not necessarily a bad thing, but it should be investigated.”

Nick Gibb, the Tory schools spokesman, called on Ofsted to investigate the findings. “Eight years ago the Government produced detailed guidelines about how much homework teachers should set,” he said. “But they failed to ask Ofsted to monitor schools’ compliance with this guidance. Such a dramatic fall in the proportion of children doing homework is a very serious indictment about standards in our schools. Ofsted should be asked . . . to report on the homework policy of the school and the extent to which it is being implemented.”

Ofsted said that it had no intention of changing inspection rules and that it did “not have a mechanised approach to the inspection of homework”.

• Hundreds of students had to sit a replacement business studies A-level exam yesterday after some attempted to cheat by reading the question papers in advance. The AQA board began an investigation and said that the would-be cheats faced disqualification.

  A spokeswoman said that about 200 business studies candidates were affected by the incident at “three or four” colleges and schools in the London area. The board had found out last week that some students had had the chance to see the paper before they were due to sit it.

  The spokeswoman said that the board had taken “immediate action and arranged for candidates in those centres to sit replacement papers”, and that the papers had not been posted on the internet.

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