A House Republican study group, analyzing Reagan administration efforts to reduce government regulation of business yesterday urged extensive new legislation to remove most remaining controls.

The Task Force on Congressional and Regulatory Reform of the House Republican Research Committee, which reports to the GOP leadership, called for legislation to eliminate the Interstate Commerce and Federal Maritime commissions, permit interstate branch banking, accelerate decontrol of natural gas prices, force the Postal Service to face competition, and revise the Clean Air Act to increase industry's flexibility.

The group also suggested modification of the so-called Delaney amendment, which requires that any additive found to cause cancer in animals be banned from human consumption, to provide for "consideration of whether data derived from animal models are relevant."

In general, the group said, "within the administration and at individual regulatory agencies pro-competitive attitudes and reduced government interference have begun to return some consumer decision-making back to the marketplace where it belongs. However, agencies are often hamstrung by their enabling statutes and cannot allow competition to operate where market conditions permit, so their administrative changes fail to provide lasting reform."

The task force, headed by Rep. Jerry Lewis (R.-Calif.), gave the Reagan administration considerably higher grades for its deregulation efforts than did a similar analysis by the conservative Heritage Foundation.

Lewis said the administration had gone about as far as it could under existing law.

"Obviously," he said, "in only two years the administration and the agencies could go only so far to reform government regulation. Certainly the administration realizes that outdated regulatory systems and myriad of ill-conceived rules and regulations are costly both in monetary and human terms. Now it is time for Congress to enact lasting regulatory reform that will benefit all consumers."

Already, the task force found, legislation deregulating the trucking, intercity-bus and railroad industries have benefited both shippers and consumers with improved service and lower transportation costs.

The railroads, partially deregulated by the 1980 Staggers Act during the Carter administration, should now "be given the freedom to charge market prices for their services," and the Interstate Commerce Commission should be "sunsetted," the report said.

The report was critical of the Federal Communications Commission, which it accused of bungling at least two opportunities to increase competition and offer consumers greater choices.

The FCC "missed a golden opportunity" to enlarge the number of AM radio broadcasting outlets, the report said, by refusing to reduce spacing on the AM broadcasting channel.

The FCC also undermined competition in the new field of cellular radio by "reserving half the frequencies in each major metropolitan area for the local wireline telephone company," the report said.

The task force also said competition in the maritime industry should be encouraged not by expanding the antitrust immunity of the merchant marine fleet--as the industry wants and as the House voted to do last year--but by letting the "competitive forces of the marketplace" determine shipping rates and letting the Defense Department pick up some of the cost of maintaining a subsidized U.S.-flag fleet.

The task force also proposed:

* That the Occupational Safety and Health Administration be directed to emphasize "health and safety education and information," rather than inspection and enforcement.

* That the Consumer Product Safety Commission be made part of a cabinet department, such as Commerce or Health and Human Services.

* That the Foreign Corrupt Practices Act be modified to "make it clear that only a knowing failure to comply with recognized accounting standards can be a basis for liability."