A head with asbestos-related cancer is taking his former local authority to court claiming he was exposed to potentially deadly fibres while fixing the school boiler.

Robert Fleming, 71, from Darlington, has mesothelioma, a form of lung cancer whose only known cause is asbestos. His solicitor, Neil Wilkinson, said an increasing number of teachers were contracting the disease, normally linked with heavy industry.

Mick Lyons, NASUWT representative for the North-east, said the problem was a “time bomb” for teachers who have worked in buildings containing asbestos.

Figures show that each year 147 people in schools, half of them teachers, died of mesothelioma between 1991 and 2000. Mr Fleming said he was exposed while he was head at Tudhoe Grange comprehensive near Spennymoor, County Durham, from 1976 to 1990. He has begun proceedings against Durham council.

Mr Fleming, whose cancer was diagnosed in December 2004, said: “I was at the school a long time and there were no asbestos awareness policies. I was certainly taken aback when it was made known to me that I had been working in those conditions.”

Mr Wilkinson said: “There were problems with the heating and Mr Fleming used to try to tinker with the boiler to get it to work.”

A Durham council spokesman said: “We do not comment on compensation claims or legal actions brought against the authority.”

Mr Lyons said: “School buildings put up in the late 60s and early 70s had asbestos in them. The total lack of funding in the 1980s led to disrepair.

It is a time bomb. Exposure is a long-term thing and we’ll be seeing a lot more cases.”

Mesothelioma among teachers may be more common than figures suggest because it can be misdiagnosed as lung cancer, Mr Wilkinson said. A cluster of claims from teachers with asbestos-related cancer has emerged in the North-east, probably because the area’s shipbuilding and mining heritage has made doctors more aware of the disease.

Eight staff in Northumberland, Gateshead, North Tyneside, Sunderland and County Durham are seeking compensation from local authorities after contracting asbestos-related cancers. Four claims against Gateshead council dating from 2001-2003 were settled out of court or without a payout.

Use of asbestos in schools has caused concern since it emerged that using drawing pins to mount displays could expose fibres.

Research by Robin Howie, an occupational hygiene consultant, found that removing one pin from an asbestos board can release 6,000 fibres. In theory, a single fibre can cause a tumour. This has prompted new guidelines this year ensuring staff know where asbestos is in school buildings.

Blue and brown asbestos were banned in construction in 1985, but asbestos cement was not outlawed until 1999.

In 2004, the National Union of Teachers secured pound;135,237 from Greenwich council, south-east London for the family of Shirley Gibson, who died of mesothelioma in 1993, aged 37. An inquest found that her disease probably arose from her work at Plumstead Manor school.