The guidance, which advises teachers they can intervene physically if pupils are being disruptive or threatening, was intended by the Department for Education and Skills to reinforce teachers’ authority in the classroom.

But lawyers, who are being contacted by growing numbers of confused staff, said it could leave them open to charges of assault.

Dai Durbridge, education lawyer at the firm Browne Jacobson, said: “In the current climate, any teacher considering the use of force is taking a serious risk and will still have to justify the steps they took in the aftermath.

“It would be for the teacher to show the force they used was reasonable.

Without more detailed guidance to fall back on, the situation is dangerous.”

Lawyers have complained that part of the advice, which tells teachers they can intervene if pupils are compromising “good order and discipline”, is “too vague” to offer protection against litigation.

Christine Betts, a senior education lawyer with the firm Veale Wasbrough, said: “We would advise caution. At the end of the day, it is still down to judges what constitutes reasonable force.”

The guidance coincided with the introduction of powers by the Education and Inspections Act, which come at a time of increased fear of litigation.

Last week, the Government advised schools to take out insurance in case weapons searches resulted in charges of assault.

In January, Ray Tarleton, a Devon headteacher, was investigated for assault after grabbing a boy seen pushing another pupil. He was subsequently cleared.

Mick Brookes, general secretary of the National Association of Head Teachers, said: “We advise that physical restraint should always be a last resort.”

A DfES spokeswoman said: “This is a broad power - necessarily so, as the reasonableness of using force has to be judged according to the circumstances of the individual case.”