The Central Intelligence Agency conducted a background investigation of an American journalist to whom it supplied material from agency files in 1970 on the late Chilean President Salvador Allende.

Charles A. Briggs, the information review officer for the CIA's deputy director of operations, acknowledged that the agency conducts similar investigations of businessmen and academic figures - without necessarily informing them of the process - with whom it has contacts.

In the case of the journalists, who was not identified, the CIA provided biographical material on Allende, who was killed in a 1973 coup, and reports on activities of Allende's Popular UNITY Party in the 1970 Chilean elections. Briggs testified in a deposition that the journalist had been given security clearances in February, 1954, December, 1968, and October, 1973.

Briggs also said that typically the journalist would not inform anyone - "his publisher or anyone else" - that the material had originated with the CIA. "The arrangement was between the individual and the agency . . .," the CIA official said.

The comments were made in the course of a deposition by Morton H. Halperin and Mark H. Lynch of the American Civil Liberties Foundation last June 21 in U.S. District Court here.

It raises a new aspect in the public controversy over the CIA's relations with journalists and persons of other professional backgrounds with whom it has contact.

A CIA spokesman said yesterday that "if for any reason there was going to be a passage of classified material, whether to a journalist or anyone else, there would be a background investigation."

Otherwise, he said, "I can't imagine any situation in which we would conduct a background investigation on a journalist or any other individual with whom we have a noncontractual relationship." He recalled that under guidelines enunciated by former CIA Director George Bush the agency also has no current arrangements with "accredited U.S. correspondents."

In the case of the Chile documents and the unidentified journalist, the CIA official testified that the documents were not themselves classified but the fact that they originated from the agency was secret. Briggs said the CIA had satisfied itself the journalist would not disclose the source.

Last April the U.S. Court of Appeals here held that the CIA exceeded the bounds of its charter when it conducted an extensive five-year investigation of a former National Student Association leader, Gary A. Weissman, as a candidate for recruitment.

"A full background check within the United States of a citizen who never had any relationship with the CIA is not authorized, and the law enforcement exemption is accordingly unavailable," the court said.

Halperin initially filed his freedom of information action on the basis of a finding in the Senate Intelligence Committee report on convert operations in Chile that "special intelligence" and "inside briefings" were provided to U.S. journalists by the CIA concerning political developments in Chile during 1970. The Senate report cited CIA documents indicating that "briefings requested by Time and provided by the CIA in Washington resulted in a change in the basic thrust of the Time story on Allende's Sept. 4 victory and in the timing of the story."

In an earlier affidavit Briggs had said that the documents in the case "were prepared in 1970 in response to a request for a limited press background briefing on the political situation in Chile."

In the deposition he testified that information was provided on the journalist "because he was trustworthy, because we had determined, through the clearance process that, according to the procedures, he was - could receive information."

Briggs declined to respond when he was asked whether the journalist was a Time correspondent. ACIA attorney sais the basis, of Briggs' refusal to answer was a prohibition "from identifying sources and methods as part of the intelligence tradecraft process who engage in confidential relationships which we have to honor or people won't be helpful."

Halperin and Lynch are now seeking court permission to take depositions from the journalist and the CIA official who provided the documents under an agreement that would place their identities under protective custody.