The Federal Trade Commission yesterday proposed cutting back on the number of proposed mergers or acquisitions reviewed by the federal government for possible anticompetitive effects.

The proposal would reduce the number of transactions reviewed by changing the rules about which transactions must be reported. It comes as the Reagan administration begins a separate study of existing antitrust laws to determine if they should be modified.

The FTC proposal would change the rules that require individuals or companies to notify the government of a proposed merger and to wait a specified period of time before completing the transaction. The reporting and waiting period allows the FTC or Justice Department to review a proposed merger to determine if it might reduce competition, in violation of federal antitrust laws.

FTC staff said the agency's proposals would lower the number of pre-merger notifications by narrowing the range of acquisitions that must be reported, requiring fewer documents and less information, and clarifying the meaning of the existing rules.

The FTC said the changes would lower the costs of antitrust enforcement by eliminating many unnecessary pre-merger reports by small firms and much unnecessary documentation.

About 1,400 proposed mergers were reported to the government in 1984, up from 1,100 the year before. So far this year, almost 1,200 proposed mergers have been submitted for federal review.

The FTC cannot estimate how many reports would be submitted if the rules are changed, or how many would have been cut from previous years, because the degree of merger activity varies with economic trends, said Roberta Baruch, a deputy assistant director in the FTC's bureau of competition.

But about 100 pre-merger reports a year would be eliminated with one proposed change, Baruch said. That proposal would require a pre-merger report of the acquisition of enough stock to control a firm only when the firm, including all its controlled subsidiaries, has annual net sales or total assets of $200 million -- up from the current reporting threshold of $25 million.

Only about 10 percent of all pre-merger reports are made under this rule, and few of those "have raised substantial competitive problems and none have resulted in enforcement actions," the FTC proposal said.

The FTC voted unanimously to seek public comment on the proposals. However, Commissioner Patricia P. Bailey expressed "serious reservations" concerning the proposal that would increase the size of the companies on which those pre-merger reports are required. The proposed change would have eliminated those few pre-merger reports that led to some agency investigation, she said. She added that she "does not necessarily agree that the existing rate of enforcement represents the appropriate level of antitrust concern with the mergers at issue."

FTC Commissioner James C. Miller III has repeatedly called for an easing of restraints on mergers, including reporting and waiting periods, arguing that we "need a competitive market for assets and capital."

Miller declined to comment on the proposal released yesterday, but FTC spokeswoman Judith Pond said the proposal "goes along with Miller's well-known efforts to reduce the costs of compliance with regulation."