RELATIVES of workers who died of an asbestos-related cancer won a compensation fight at the Supreme Court today.

Judges ruled that insurance liability was ''triggered'' when employees were exposed to asbestos dust - not when symptoms of mesothelioma emerged.

Legal experts say the ruling by the UK's highest court means that employers' insurers will have to pay compensation claims.

Relatives of victims want to make claims on policies from the late 1940s to the late 1990s.

Families started a legal fight for compensation more than five years ago and lawyers say the Supreme Court ruling could affect thousands of claims.

Relatives won the first round of their battle in 2008, when the High Court said firms' insurers at the time workers inhaled fibres were liable.

But two years later the Court of Appeal said in some cases liability was triggered when symptoms developed - sometimes decades after exposure.

Lawyers said the appeal court ruling had left victims' families facing ''confusion and uncertainty''.

A panel of five Supreme Court justices had heard argument about a group of lead cases at a hearing in London in December and delivered judgement today.

The Supreme Court ruled that the disease could be said to have been ''sustained'' by an employee in the period when it was caused or initiated, even though it only developed or manifested itself later.

Lord Clarke said: ''The negligent exposure of an employee to asbestos during the policy (insurance) period has a sufficient causal link with subsequently arising mesothelioma to trigger the insurer's obligation.''