A group of asbestos defendant companies and insurers has declared its opposition to a Senate proposal curbing asbestos claims, and warned that industry groups working on the plan do not necessarily represent them.

The group sent a letter dated January 28 to Senate Judiciary Committee Chairman Arlen Specter, a Pennsylvania Republican, complaining the latest draft of his plan for a compensation fund to replace asbestos suits “raises serious concerns.

“We cannot currently support this legislation as proposed,” said the letter from a dozen insurers and asbestos defendant companies calling themselves the Coalition for Asbestos Reform. Copies of it were circulating on Capitol Hill.

Rather than set up a $140-billion fund, as Specter’s plan suggests, it is time to consider other solutions, the group said, such as legislation setting medical criteria for asbestos victims to bring claims against companies.

Among the signatories to the January 28 letter was American International Group Inc., an insurer that has long opposed the concept of creating a multibillion-dollar trust fund to handle claims for asbestos-caused illness.

The signatories also included Chubb Corp., General Re Corp., a unit of Berkshire Hathaway Inc. run by billionaire Warren Buffett; A.W. Chesterton Co., a manufacturer of industrial fluids; and the Associated General Contractors of America.

Asbestos was widely used for fireproofing and insulation until the 1970s. Scientists say inhaled fibers are linked to cancer and other diseases, and hundreds of thousands of injury claims have clogged U.S. courts and bankrupted companies.

Two groups - the National Association of Manufacturers’ Asbestos Alliance and the Asbestos Study Group - have worked with lawmakers for two years to try to find a legislative solution to limit asbestos liability. But the authors of the January 28 letter said these groups “do not necessarily speak for us.”

Several other businesses also wrote to Specter earlier this month to complain that the payments companies would have to make to the fund proposed by Specter would exceed the asbestos-related costs they already face.

Specter plans to hold a hearing on Wednesday on his draft legislation, examining how to distinguish asbestos exposure from exposure to another mineral, silica, which also has been blamed for causing illness in workers.