Prime Minister Tony Blair has vowed to overturn the controversial House of Lord's ruling in the Barker mesothelioma test case.

In a move that lawyers described as "unparalleled", Blair said he expected to make an announcement to change the ruling within a fortnight.

Speaking at a GMB conference in Blackpool, Blair said: "I regret that judgment. I'm looking at the moment to see the best opportunity for us to change it.

"If we can change it, we will. I hope to announce something on this in a couple of weeks."

He gave no indication as to the steps the government might take.

Blair's statements come as 50 MPs signed a Common's motion demanding a change in the law. They are arguing that the Barker ruling will deprive mesothelioma victims of compensation.

It was widely anticipated that the government would include a provision overturning the ruling in the second reading of the Compensation Bill this week.

But the parliamentary under-secretary of state for Constitutional Affairs, Bridget Prentice, only signalled support for the provision. She said: "The secretary of state and I have a great deal of sympathy with the concerns that he and others have expressed about the judgment in Barker v. Corus and... we are very sympathetic to the claimants."

Lawyers, however, said changing the law would be difficult. Alison McAdams, an associate partner with Davies Arnold Cooper said: "The Barker case featured strongly in the Compensation Bill debate so we know this is high on the agenda.

"I do not see how Barker can be overturned, so the government will need to look for a different mechanism."

"Presumably, it will be some sort of scheme to compensate victims.

"There will need to be a lot of work to see what model will be most effective and it won't happen overnight."

Insurers called on the government to consult the insurance industry.

Martin Saunders, motor and casualty manager at Allianz Cornhill, said: "This is a government which, considering the speed and pace of change, needs to embrace dialogue.

"The government is pressing the accelerator far too hard."