Academies are increasingly introducing longer working hours for teachers because of a deliberate government policy to encourage them to lengthen the school day, it was claimed this week.
The allegation was made at the NUT annual conference in Cardiff as the union voted to campaign for a new national contract to combat the fragmentation of teachers' pay and conditions caused by the huge expansion in the number of academies.
Ian Murch, NUT treasurer, told delegates: "There are examples now, particularly in academies, of changes being made to teachers' working hours with the explicit encouragement of the Department for Children, Schools and Families."
He told The TES he knew of the policy because of his involvement in negotiations with sponsors about planned academies in Yorkshire.
Government-approved consultants helping sponsors to set up academies always suggested lengthening the school day, he said.
He believed the idea came straight from the DCSF because it was voiced every time, no matter which firm of consultants was used.
Academies are supposed to be free to make their own decisions on teachers' pay and conditions and do not have to follow the school workforce agreement.
Mr Murch said: "A lot of these academies are in challenging areas where longer hours will only put more pressure on staff, who will leave."
The NUT's national contract would apply in all schools, including academies, and limit annual teachers' hours to the standard 1,265 per annum. It would also guarantee teachers a day each week out of the classroom, limits on class sizes and a term's sabbatical every seven years.
A DCSF spokesperson said: "Decisions on the length of the school day and term times would be made by the Academy Trust."