In at least four instances the Central Intelligence Agency exploited its relationship with foreign and American news media to improperly influence events and opinions in the United States, a noted CIA critic testified yesterday.

Morton H. Halperin, director of the Center for National Security Studies, a Washington-based organization critical of the intelligence community, told a House oversight subcommittee that, among other things, the CIA gave a false briefing to a representative of Time magazine on Chilean Marxist leader Salvador Allende and the political situation in Chile around the time of Allende's election as president.

A CIA copy of the briefing paper, portions of which Halperin obtained under the Freedom of Information Act, shows that it argued in considerable detail that Allende and his Chilean Communist Party sought to destroy the free press there. This Sept. 18, 1970, briefing, Halperin said, consisted of the same information the CIA was disseminating to its Latin American sources for use against Allende.

Particularly objectionable, Halperin said, were personal characterizations of Allende as a supporter of violence as a political necessity. It described him as an "extremely ambitious, very vain man . . . a symbol of sartorial splendor and capitalist amenities."

"Speaking before a disappointingly small rally in Santiago on Sept. 13," the paper said, "Allende told the [TEXT OMITTED FROM SOURCE]