Congress should write new laws to protect Americans from warrantless searches conducted in national security investigations, the Senate Intelligence Committee said in a report issued yesterday.

The report said the Foreign Intelligence Surveillance Act, which requires the FBI and the National Security Agency to obtain approval for electronic surveillance of suspected foreign agents, has worked well for the intelligence agencies, while protecting the privacy of American citizens. But it said that the protections of the warrant should be extended to physical searches of homes and opening of mail.

Such searches were conducted by the FBI in the early 1970s when hunting members of the Weather Underground.

Executive branch officials have long contended that the president has the inherent right to conduct warrantless searches in national security cases.

The report quoted a Justice Department official as testifying last year that the Reagan administration approves such searches "sparingly" and that each case receives "extremely close scrutiny."

But the Supreme Court has never considered the issue, and extending the warrant requirement to physical searches "would remove the legal and constitutional ambiguities inherent in current executive branch practice," the Senate report said.

Jerry Berman, legislative counsel for the American Civil Liberties Union, said his organization opposes the proposal because it considers any warrantless search unconstitutional.