Donald Maclean, the British diplomat who became a Soviet spy and supplied Moscow with priceless intelligence information before defecting to this country in 1951, was given a respectful funeral here today and was hailed as a "faithful son and citizen" of the Soviet state.

Maclean, 69, died Sunday, reportedly of cancer, but his death was announced in the government newspaper Izvestia only today. Without making any direct reference to his espionage activities, Izvestia described "Donald Donaldovich Maclean" as a man "of high moral qualities and a convinced communist" who "devoted all his conscious life to the high ideals of social progress and humanism" and who performed outstanding services to the Soviet state.

The tall, elegant former diplomat, whose father, Sir Donald Maclean, was a Liberal cabinet minister, was at the center of Britain's infamous spy scandal. He and fellow spy Guy Burgess fled to Moscow in 1951 just as British counterintelligence agents were about to interrogate them.

The "third man" in the affair, which led to a major shake-up of British intelligence, was Harold (Kim) Philby who tipped off Maclean and Burgess about their impending arrest. Philby defected in 1963 to Moscow, where he still lives. Burgess died in 1964.

The "fourth man" in the affair was the former Sir Anthony Blunt, who served as art adviser to Queen Elizabeth II until 1979 when he was publicly identified as a former Soviet spy and stripped of his knighthood. The four men belonged to the British establishment and became idealistic communists while attending Cambridge University in the 1930s. They later volunteered their services to Moscow.

A memorial service for Maclean was held this morning at Moscow's Institute of World Economy and International Relations, a government think-tank, where he worked as a foreign policy analyst. A large portrait and an obituary of Maclean were displayed prominently inside the institute's entrance hall but outsiders were not admitted to the ceremony.

The red-draped coffin was later taken to the city's principal crematorium on the snow-covered grounds of the Donskoy Monastery where Maclean's colleagues carried it on their shoulders in the traditional Russian ceremony. They were followed by other mourners carrying his portrait and a red cushion on which were displayed his three high decorations--the Lenin Medal for Glorious Labor, the Red Banner of Labor and the Fighting Red Banner.

One of the wreaths bore the inscription "From Comrades in Arms" and was presumably from the KGB, the Soviet Secret Police. Inside the crematorium, as an organist played funeral music, about a hundred mourners placed roses, tulips and other flowers on the coffin and an orator hailed Maclean as a faithful Soviet citizen.

"The fatherland bids farewell to its faithful son, citizen of the Soviet Union Maclean," the speaker said.

Maclean's American wife Melinda and their three children were not present. All live in the West. Also missing was Kim Philby.

Following his graduation from Cambridge, Maclean joined the Foreign Office and was first posted to Paris in 1938 as a third secretary in the British Embassy. In Paris he met the woman who became his wife.

In 1944, he was sent to the British Embassy in Washington and remained there until 1948. For the last year of his tour in Washington he was Britain's representative on a British-U.S.-Canadian policy committee dealing with the highly sensitive matters of atomic cooperation.

It is believed that he supplied Moscow with priceless information on the subject. While in Washington, he had access to secret materials of the U.S. Atomic Energy Commission.

In 1948, Maclean was promoted to a senior position at the British Embassy in Egypt, where he began to drink heavily. At one point he was arrested in a drunken condition in Alexandria and held for two days in jail.

Following that, Maclean was given a six-month leave and was transferred to London where he became head of the American Department in 1950. He was fully briefed on all aspects of U.S.-British relations, including developments in the Korean conflict, which he was able to pass on to Moscow.

The following year, suspicions about numerous leaks narrowed down to Maclean as a possible Soviet agent. Warned by Philby, who had joined British intelligence in 1940, Maclean and Burgess fled to Moscow.

Suspected of warning the defectors, Philby had to resign, and became a newspaper correspondent in the Middle East.

Maclean, who took Soviet citizenship, worked for many years at the institute and published extensively under a pen name. He had been ailing for some months and was hospitalized in early January.

Philby, in his book "My Secret War," provided some insight into the kind of information the espionage ring gave the Soviets. He said he had been briefed in great detail by Allen Dulles, then director of the Central Intelligence Agency, about a clandestine operation being mounted against the Albanian government.

Philby said Dulles outlined to him all the contingencies involved, adding that the Americans had considered every aspect of the operation to ensure its success--except the fact that "within two hours" the entire plan would be on the desk of Philby's intelligence boss in Moscow.