The FBI's retiring counterintelligence chief said yesterday that five communist-bloc diplomats were quietly forced to leave the United States in the past year after they were caught spying.

William Cregar, head of the bureau's intelligence division, said that such expulsions usually are not publicized because the communist nations would feel compelled to retaliate.

Cregar's remarks capped a recent series of exposures by American and allied intelligence officers of Soviet-bloc spy networks in New Zealand, Canada, Spain and Japan.

It has been suggested that the stream of disclosures in part of a U.S. policy decision to change the usual rules of international spying and retaliate against the Soviet Union for its invasion of Afghanistan.

Spokesmen for the State Department and Central Intelligence Agency refused to comment on the matter yesterday. A White House official said he was unaware of any policy change. But it seems clear that at least some of the disclosures were orchestrated.

Last month, for instance, John McMahon, the CIA's deputy director for operations, told a House Intelligence subcommittee in closed session about Soviet forgeries of U.S. government documents. Last week, the testimony was suddenly made public, exposing to public view more than 100 pages of examples of alleged Soviet-bloc propaganda.

The release was to "dramatize" recent increases in such forgeries, a subcommittee spokesman said.

The Chicago Tribune reported on Monday that the CIA has disclosed the names of many Soviet-bloc agents of influence to allied intelligence in recent weeks.

In his testimony, McMahon noted that a forged U.S. Army field manual -- purporting to show plans for American interference in allies' domestic affairs -- showed up in Spain in 1977 in the hands of a Cuban intelligence officer. The Tribune story said the CIA gave the names of those involved in the fabrication to Spanish intelligence.

Another exposure of a Soviet espionage network occurred in January in New Zealand, where Soviet Ambassador Vsevolod Sofinsky was expelled after he was accused of funneling money to a socialist political party.

In retaliation, the Soviets expelled the New Zealand ambassador from Moscow a month before the end of his scheduled tour of duty.

In Canada in January, two Soviet embassy officials were expelled after being charged with paying money to an American undercover agent.

In Japan, the army's chief of staff resigned after a Soviet-run spy network was closed down by police.

Intelligence officials refused to say yesterday whether these events were connected.

There has long been a dispute within the intelligence community about how to treat foreign diplomats caught as spies. The traditional theory is the one the FBI's Cregar noted yesterday: expel the person quietly so the other country doesn't feel compelled to respond in kind.

There's another argument against even quietly expelling the discovered spy, intelligence officials note. At least you know who he is and can monitor his activities. If he's kicked out, he'll be replaced by someone your counterintelligence will have to find all over again, they said.

Last fall, in the wake of the controversy over the Soviet brigade of troops in Cuba, columnist Jack Anderson reported that national security affairs adviser Zbigniew Brzezinski was quarreling with Secretary of State Cyrus R. Vance about taking a hard line in generating anti-Soviet propaganda around the world.

In a press conference at the time, Vance took pains to say there was no dispute between State and Brzezinski. He didn't deny the anti-Soviet campaign was being considered, however.

The last publicized expulsion of a Soviet diplomat from the United States occurred in 1978. Vladimir P. Zinyakin, an official at the Soviet mission to the United Nations, was forced to leave for his role in a spy case.

The case involved two Soviet employes who didn't have diplomatic immunity and were prosecuted for buying U.S. defense secrets from a Navy officer cooperating with the FBI.

Attorney General Griffin B. Bell decided to press the case to show the United States wouldn't tolerate spying by non-diplomats at all.

The FBI's Cregar said yesterday that he feels the FBI has made excellent progress in its silent counterintelligence battle with communist-bloc spies.

"We know more about their methods of operation. We have a better appreciation of who their intelligence officers are and of the equipment and techniques they are against us," he said.