A MAJOR legal challenge is to be made by a York law firm on Wednesday, to clarify how insurance companies should treat claims relating to asbestos deaths at businesses where their employers' liability policies have been in force.

National personal injury practice, Corries Solicitors, of Navigation Way, York, which has the biggest dedicated asbestos team in the UK, is taking a case to the Civil Justice Court at Birmingham High Court.

It is almost certain to become a test case into how insurance companies address liability for asbestos-related deaths. And the outcome will be carefully monitored by the York Asbestos Support Group.

Abestos-related illnesses are a deadly legacy of the thermal material's widespread use in building projects throughout the 20th century. It can take between ten and 50 years for deadly tumours such as mesothelioma to develop.

The need for the legal challenge has arisen in the case of a Staffordshire widow, Mrs Sylvia Gilligan, 69, whose husband Anthony - known as Fred - died in 2003, aged 71, from mesothelioma.

Mr Gilligan, a joiner, is alleged to have been exposed to asbestos while working for Holland Hannen & Cubitt (Midlands) Ltd on the building of Hanley Telephone Exchange between 1972 and 1974.

The High Court challenge will be mounted against the two insurance companies which provided cover for now-defunct Holland Hannen and Cubitt in the 1970s, when Mr Gilligan worked for them, and ten years ago, when his tumour is believed to have developed. Both deny liability under the wording of their policies. Insurance company Excess, which provided employers liability insurance to Holland Hannen & Cubitt during the 1970s when Mr Gillgan worked for them say that their policy refers to illness or injury "sustained" during the lifetime of the policy and that they are not responsible for the tumour which developed years later.

Zurich, which provided cover in the 1990s, claims that its policy covers only injury or illness caused by a negligent act during the lifetime of the policy and not ten or 20 years earlier when Mr Gilligan was exposed to the asbestos.

The court action, being brought by Dominic Collingwood, of Corries, will seek a ruling against Holland Hannen & Cubitt which will allow proceedings under third-party rights against insurers' legislation in a bid to force Zurich, Excess or both companies to accept liability.

He said: "The actions of Excess and Zurich in this case are a new impasse in the thousands of claims we handle each year, which could lead to deadlock in many other cases where people have lost loved ones and been robbed of financial support."

Kim Daniells, founder of the York Asbestos Support Group, said: "It is unlikely that the outcome will affect the many workers in York who contracted the disease after working at big engineering firms in the city like BREL, because these companies were either backed by state industries or had adequate insurance cover at the time.

"However, there may be York and North Yorkshire people affected by asbestos-related diseases who worked for smaller companies which have since vanished. We will carefully monitor the hearing's result."