Insurers have begun an unprecedented move to overturn a Scottish Parliament Act that allows compensation for asbestos exposure. If their interim interdict in the Court of Session is successful, it will be the first time that the courts have intervened to prevent legislation passed by Holyrood being put into practice.

At the heart of the argument is whether pleural plaques on the lung cause suffering. Also at stake is the longstanding legal principle of delict, which decrees that if someone suffers an injury they are entitled to compensation.

The insurance industry argues that the new Act, passed by MSPs last month by 98 votes to 16, contravenes the European Convention on Human Rights and insurers' economic rights. It argues that the decision at Holyrood to approve the Act overturned a fundamental UK legal principle that compensation is payable only where physical harm has been suffered through negligent exposure to a risk.

The landmark House of Lords ruling on asbestos, in the case of Rothwell in 2007, was that the existence of pleural plaques - a thickening of lung membranes - was not in itself something for which people could claim compensation.

The financial implications are enormous, especially as asbestos still exists in schools and hospitals. Insurance actuaries estimate that there could be 6,000 claims a year in Scotland, and payouts could range from £76million to £607million.

The new Act was passed despite Tory opposition and strong warnings from insurers, who said that it ignored medical opinion and would “open the floodgates” for claims. The four companies bringing the action in the Court of Session to block the Damages (Asbestos-related conditions) (Scotland) Act are Aviva, AXA Insurance, RSA and Zurich, who represent half the employers' liability market.

The insurers say that the Act makes pleural plaques a compensatable condition in Scotland, ignoring the fact that plaques are symptomless, do not affect health or lead to asbestos-

related diseases, such as mesotheli- oma. They say that the Act fails to assess fully the financial impact on Scottish companies and taxpayers and could lead to a rise in claims from people exposed to a risk, but who have no symptoms. This would mean higher insurance costs for all companies and damage the economy.

Their contention is that the Act effectively overturns the law of delict. However, legal sources in Scotland said yesterday that if the insurers' action was successful, it would re-write the principle of delict by denying compensation to those who had been injured by negligence.

Malcolm Tarling, from the Association of British Insurers, said: “This could create a precendent where if people are exposed to risk, but have no symptoms, they could sue for compensation. It is about the potential for many claims which this Act could open out. We are fundamentally opposed to any move that will extend compensation to those exposed to a risk but not suffering any symptoms.”

The Act is due to come into force in June. The insurers say that regardless of whether this interim interdict is successful, a judicial review hearing will go ahead this year.

The Scottish government said that it was disappointed and would vigorously defend the action. A spokesman said: “The insurance companies' action may delay, but will not ultimately defeat, our resolve to defend the rights of people who have been negligently exposed to asbestos.”

The landmark decision on establishing the duty of care, for Scotland and for the rest of the United Kingdom, is the House of Lords appeal case, Donoghue v Stevenson 1932 - the case of the snail in the bottle. A Mrs Donoghue was in a café in Paisley where she consumed a ginger beer float that contained a decomposing snail in an opaque bottle. She suffered serious gastric problems as a result.

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