The High Court is about to release a decision on after-the-event (ATE) insurance that it is claimed will dwarf Callery v Gray's importance to insurers and claimants.

Lawyers said at least 100,000 cases were held pending the Chief Cost Master's judgment, which is expected later this month.

Colman Coyle is handling a group of 20 test cases brought by Claims Direct claimants against seven insurers, including Norwich Union (NU), Groupama and AXA. Joint senior partner Howard Colman said the claimants were attempting to recover the £1,215 ATE premium they paid Claims Direct. The policies were underwritten by a number of Lloyd's syndicates.

"When a case is successful, the claimant is entitled to recover its ATE insurance premium from the defendant," Colman said.

"These are all successful claims, but the defendants said they weren't prepared to pay that much for the premium."

He said the defendant insurers agreed to settle the claimants' damages and costs, but had suggested to the court that it should pay £100 to £200 of the total premium.

The test cases represented a wide variety of claims, including road traffic accidents, and slip and trips, with damages from small amounts to £30,000.

Colman said, whatever the judgment, it seemed inevitable that it would be appealed.

"There are vast sums of money at stake, with a difference of around £1,000 per policy and at least 40,000 claims, and some say as many as 100,000, pending," he said.

He said the judgment would have a significant impact on all ATE and liability insurers and claims management companies.

The Callery v Gray judgment was widely described as disappointing in its failure to resolve contentious ATE issues such as the reasonableness of premiums.

Berrymans Lace Mawer joint national head of insurance liability Martin Bruffell said he had no doubt there would be many more test cases, since the House of Lords had sent insurers and claimants "back to square one".