Clair E. George, who headed the CIA's covert operations directorate during the Iran-contra affair and was criticized in last week's congressional report, announced yesterday that he will retire at the end of the year.

George, 57, a 32-year intelligence veteran, has been talking about retirement for several months and told one friend recently that he "was reading the handwriting on the wall." Central Intelligence Agency officials yesterday described George's retirement as voluntary.

George's impending departure will remove one of the key holdovers from the six-year tenure of the late CIA Director William J. Casey. His retirement decision came just weeks before CIA Director William H. Webster has said he will respond to the Iran-contra affair with possible personnel changes, and a day after he said he will keep Robert M. Gates as deputy director. Webster has been under pressure from Congress to clean up the CIA in the wake of the Iran-contra debacle.

The leaders of the Senate Select Committee on Intelligence rebuked the Directorate of Operations, which George heads, in an addendum to last week's Iran-contra report.

Two senior CIA officers in Central America from the directorate secretly supported the contras "in a manner contrary to both agency policy and restrictions imposed by law," said Sen. David L. Boren (D-Okla.), the Senate committee chairman, and Sen. William S. Cohen (R-Maine), the vice chairman, resulting in "a breakdown in the process of supervision and accountability."

In the Iran initiative, the two senators criticized the flawed recordkeeping in the directorate and George's acquiescence to the use of an inexperienced agent-handler to deal with key Iranian middleman Manucher Ghorbanifar.

"Career officials were reluctant, unduly suppressed or ineffective in bringing their concerns to the attention of management," the two senators said.

George, whose title is deputy director for operations or DDO, supervises all covert operations, agency clandestine intelligence gathering and CIA stations abroad. The post is considered one of the most important and powerful in the government.

George was head of CIA congressional relations in the spring of 1984 when the CIA's role in secretly mining Nicaraguan harbors was exposed. The Senate intelligence committee complained it had not been fully informed of the controversial mining, and some blamed George. Casey, realizing that George's effectiveness on the Hill was ended, promoted him to DDO in June 1984.

Yesterday Webster praised George for serving "his country and this agency with courage for over 32 years, often overseas and often in the most demanding circumstances." He noted that George, who had served as Beirut station chief in the mid-1970s, took over as the Athens station chief from Richard Welch who had been assassinated in 1975.

One of George's key station chiefs, Tomas Castillo in Costa Rica, testifed in the Iran-contra hearing that because of guidance he received from George, he misled the CIA inspector general, Carroll Hawver, who was investigating the contra resupply operation. George has denied giving such guidance. Castillo was a pivotal link in Lt. Col. Oliver L. North's resupply operation and assisted in delivery of lethal supplies to the contras when Congress had banned them.

The second CIA official singled out by Boren and Cohen was the base chief at a contra camp in Honduras. Congressional investigators discovered he had authorized delivery of military equipment by CIA helicopters to contra forces inside Nicaragua in violation of regulations. He also failed to tell the truth about his operations to the CIA inspector general.

In October 1986, after the contra supply plane with cargo handler Eugene Hasenfus aboard was shot down, George was present when misleading testimony was given to the House Permanent Select Committee on Intelligence by Assistant Secretary of State Elliott Abrams.

George later apologized to the committees, saying, "I didn't have the guts" to contradict Abrams.

Another senior CIA veteran involved in the Iran-contra affair, Duane R. (Dewey) Clarridge, has also told friends he is thinking about retiring early next year. As European division chief in late 1985, Clarridge has insisted that he was not aware that a key Iran arms shipment included weapons at a time his CIA office was command post for the delivery.

Alan D. Fiers, chief of the Central American Task Force, is also the subject of various Iran-contra investigations. North and Castillo have testified that Fiers knew about the secret resupply effort. Fiers has denied that he knew of Castillo's until late last year.

The Los Angeles Times, quoting U.S. officials who declined to be named, reported yesterday that CIA Inspector General Hawver disclosed to the agency's staff that he will resign at year's end. CIA spokesman Sharon Foster said that the agency could not confirm or deny that report.