Asbestos was used extensively in schools built between the Second World War and the early 1980s and an estimated 13,000 schools in the UK could contain the material.

The Association of Teachers and Lecturers (ATL) claimed that slamming a classroom door or putting a pin in a wall in some of these schools could be fatal.

The union is calling for Ministers to launch a national survey of all schools and colleges to discover the extent of asbestos use in buildings.

ATL general secretary Mary Bousted, said: "We are deeply concerned about the continuing risk to teachers, support staff and pupils from asbestos.

"We don't know how many schools still contain asbestos, so most teachers have little idea of whether they or their pupils are being exposed to it.

"Over 400 ATL members know they have been exposed to asbestos in their school. But this is the tip of the iceberg."

In 2002 an inquest into the death of retired teacher Jean Whitwam, from Quarmby, Huddersfield, found that she died after breathing in asbestos while she was working at Outlane Infant School in the town between 1969 and 1993.

Mrs Whitwam, 66, died from mesothelioma, an industrial disease from asbestos fibres.

Delegates at ATL's annual conference next month will call for all asbestos to be removed from schools by 2010.

Between 1980 and 2000, 182 people working in education in Britain died from mesothelioma, the union said.

A spokesman for the Department for Children, Schools and Families said the union's warning about drawing pins was "irresponsible, scaremongering".

Meanwhile tests at one school found asbestos levels up to seven times the legal limit, it was reported last night.

Experts said large amounts of asbestos could be released into the air if children at Hay Lane School in Brent, north-west London, banged into ceilings or walls, according to ITV News.

Brent Council said in a statement that the Health and Safety Executive had confirmed the school was safe for occupation.