Assistant general secretary Mike Clancy said: "This totally ignores the suffering endured by these victims and their families who, following the diagnosis of pleural plaques, live with the continual fear of developing a life-threatening respiratory disease.

"Pleural plaques are the result of negligent exposure to asbestos. This decision means that employers who have either intentionally or unintentionally put their employees at risk cannot now be held to account."

The union warns that the current incidence of asbestos-related disease is only the tip of the iceberg. Prospect’s own asbestos register, which allows members to record details of any occupational exposure to asbestos, has received over 1,200 entries since 2001.

Similarly national figures for mesothelioma alone – a rare form of cancer that affects the lining of the chest – show that the number of reported deaths has risen from 153 in 1968 to over 2,000 a year by 2006, and look set to peak at 2,500 per year over the next five to 10 years.

Said Clancy: "We can only guess at the number of people who will be denied redress as a result of this ruling for the suffering they and their families have endured because of occupational asbestos exposure. Prospect will be working with the TUC to lobby government to reverse the decision."

Pleural plaques are areas of thick scar tissue that form in the chest lining and diaphragm as a result of asbestos exposure.

Over time, this thickening of the pleural membrane, which lines the lungs, can make breathing difficult and be accompanied by the development of serious respiratory diseases including mesothelioma and lung cancer.

Prospect represents 102,000 scientists, professionals, managers and engineers, including dockyard and electricity industry employees where asbestos was widely used until the 1990s.