Federal workers would be required to join Social Security under legislation introduced by Rep. Barber Conable (R-N.Y.).

He is ranking minority member on the House Ways and Means Committee, which handles tax legislation and is looking for ways to pump more money into the financially ailing Social Security system. Uncle Sam's 2.8 million workers, who have their own retirement system, and about 5 million state and local government aides are the last big group of employes outside the Social Security system.

Conable has introduced the mandatory Social Security plan before. But it could fly this year. Several blue-ribbon groups have recommended that federal, state and local workers be required to join Social Security. The President's Pension Policy Commission, appointed by Jimmy Carter, recommended on Feb. 26 that public employes be required to join. It also said the federal government's retirement age should be raised and that federal and military retirees be limited to one COL (cost of living) raise per year. President Reagan has already recommended that Congress wipe out the March and September inflation adjustments for U.S. retirees, to give them a single annual COL catchup.

Conable says his bill (H.R. 1018) would give U.S. employes better disability and survivor benefits than they enjoy under their own staff retirement system pays significantly better benefits that Social Security, and at an earlier age. But U.S. workers pay more for their system than do people under Social Security. And the civil service retirement benefits are taxable; Social Security is not.

Reagan has proposed some significant cutbacks in Social Security benefits and the majority of federal and postal workers want no part of mandatory Social Security, according to polls and their unions.

The Reagan administration has not yet taken a stand on mandatory Social Security coverage. Conable's bill would make coverage mandatory beginning in January 1983. It would be up to the Post Office-Civil Service Committee to determine if current, long-service federal and postal workers would have to shift to Social Security or could remain in their own pension plan. And it would be up to the committee, headed by Rep. Bill Ford (D-Mich.), to decide what sort of supplementary civil service retirement program would be kept, and what it would cost, for federal workers.