No teacher should be allowed to work full-time as a union representative in a state-funded school, according to a government clampdown on “facilities time”.

Teachers who also hold positions with trade unions should spend the majority of their time in the classroom, according to guidance published today by the Department for Education (DfE).

Employers will also be asked to keep detailed records of how much they are spending on funding teachers to carry out union work, which unions insist can save money by preventing full-blown industrial disputes.

The guidance comes following a review of facilities time spending in government, which led to all full-time union representative posts being axed from the civil service.

There have been several high-profile cases in the past where it has emerged that a number of local authorities were paying considerable bills for union representatives to carry out their work.

In one area, according to the DfE, approximately 10 full-time equivalent classroom teacher union representatives received taxpayer funding of nearly £400,000 in 2011-12.

But a report by the Trades Union Congress, published in January 2012, estimated that facility time saves the public sector between £223 million and £586 million a year.

Malcolm Trobe, deputy general secretary of the Association of School and College Leaders, warned that cuts could mean that unions will not be properly funded.

“The guidance clarifies a number of issues related to the use of facilities time but it does raise questions about whether the level of funding will be sufficient,” he said. “We are also concerned that there will not be sufficient flexibility to allow for local requirements.”

In a consultation on the issue last autumn, the Association of Teachers and Lecturers union said: “We do not question the wisdom of union reps maintaining a link with the classroom, but we do not accept that this should mean a blanket ban on union reps, especially local authority reps, being seconded to carry out union duties across a local authority on a full time basis.

“It may suit all parties for there to be a single point of contact for a particular local authority.”

But David Laws, schools minister, said today: “Teachers are paid to work in the classroom. Clearly effective representation of teachers can play an important role in our schools, but taxpayers’ money shouldn’t be funding trade-union representatives who spend little or no time actually teaching.

“This advice has widespread support from the sector and will provide greater clarity, transparency and accountability about how this money is used, and how it benefits schools.”