Grant-maintained school heads who are alarmed at the cost of providing cover for teachers on maternity leave may have their staff assessed for the likelihood of pregnancy.

Both the Department for Education and Employment and the Funding Agency for Schools have been under pressure from opt-out heads for help on meeting the cost of maternity cover. They have been pressing for a special Government grant to pay for cover while staff are on maternity leave and claim budgets can be badly skewed by having to pay out for replacement staff, particularly in small primary schools.

But the FAS - the quango set up to administer finance for the opt-out sector - ruled out such a move.

A spokesman said: “There is no extra pot of money that we can dip into. Any extra grant would be at the expense of something else.

“Maternity cover is something you have to budget for. It is possible to get people like accountants in to assess the likelihood of losing staff on maternity.”

GM schools receive a sum of money for maternity cover in the extra cash they are given to compensate for the loss of central services when they leave council control.

But Cecil Knight, chairman of the Grant-Maintained Schools Standing Advisory Committee, said: “In small schools that doesn’t necessarily equate to what is needed.”

Mr Knight, head of Small Heath School, Birmingham, said: “In a small school where quite by chance a couple of people go on maternity leave at the same time you have to find replacement staff and that places a strain on your budget. ”

The FAS is now producing a maternity guide for opt-out schools which details employment practice and how to reclaim maternity pay from social security departments.

GM Schools Mutual - the sector’s insurance company - has been investigating the possibility of a special insurance policy on maternity cover but Derek Archer, an underwriter, said: “We haven’t come up with a solution.”

Problems over maternity cover are particularly acute in the primary sector where women make up 81 per cent of the 178,773 workforce across both local authority and grant-maintained schools. Of that 81 per cent, nearly half the women are aged between 20 and 39.

Mr Archer said: “A school that has more young, female teachers is more likely to have staff applying for maternity leave. If you get a school’s staff profile and history it could be possible to extrapolate the likelihood of staff becoming pregnant, but how scientific or accurate that is I don’t know. ”

Zurich Mutual, the market leader in local authority cover, said it did not provide cover for maternity leave. Supply teacher policies, where schools are paid around Pounds 100 a day towards the cost of replacement staff, specifically exclude maternity leave.