Almost nine out of 10 British school buildings contain potentially deadly asbestos, yet experts warn it would cost too much to remove it all.

Figures from Freedom of Information requests to local authorities show 86 per cent of all schools in the country contain the killer dust, far higher than previous estimates.

Professor Julian Peto, one of the country’s leading experts on asbestos, said removing it all was not an option as it would “only save” around 25 lives a year in 50 years’ time when effects of asbestos on pupils will take hold.

He said: “You cannot rebuild all the schools in Britain to prevent about 25 deaths a year.

“These are deaths that will occur predominantly over the age of 70.

“You have to remember that is the effect of childhood exposure.”

However Michael Lees, 67, founder of the campaigning group Asbestos In Schools, who obtained the figures, argued: “We expose a large number of children to asbestos in schools and this is contributing to the terrible death toll.

“Successive governments brushed this under the carpet because the disease can take decades to develop.”

Mr Lees, a father of two, from north Devon, lost his wife Gina, a primary school teacher, in 2000 when she died aged 51 from mesothelioma.

Last week a review ordered compulsory asbestos training for teachers.

Mr Lees said: “The review is a step in the right direction and future policy can be built on it, however it does not go far enough.

“We accept removing asbestos from all schools can only be done over a long period.

“We believe the Government should adopt long-term policies to eventually eradicate all asbestos from schools.”

Latest figures show 2,535 deaths a year from mesothelioma in Britain, the highest rate in the world and more than all UK road deaths. Of these 300 are attributed to schools.

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