Britain scrambles to plug intelligence leaks

Britain's NATO allies, led by the United States, are insisting on quick, firm action to stop damaging espionage leaks here to the Soviet Union. As a result, the government of Prime Minister Margaret Thatcher has begun to take fresh steps. It may be forced to take even more.

Government officials here admit security breaches have caused deep concern and damage since World War II. Far too many British officials have turned against Western ideals in favor of Soviet communism.

They range from senior diplomats Kim Philby, Guy Burgess, and Donald Maclean to the more recent cases of art historian Anthony Blunt, Leo Long, Army Lance Cpl. Philip Aldridge, and Geoffrey Arthur Prime, the Russian linguist who worked at the top-secret Government Communications Headquarters in Cheltenham, which eavesdrops electronically on Soviet satellite and other signals.

Now come the latest revelations that Michael Bettaney, the MI5 agent in charge of ''K Branch,'' which runs counterespionage against Soviet agents in Britain, had been trying to feed highly sensitive data to a Soviet diplomat in London.

Lord Chief Justice Lane indicated when passing sentence April 16 that Bettaney would not have hesitated to reveal names of British agents, a move that would have led to those agents being killed.

Bettaney has now begun a sentence of 23 years. He leaves behind a defiant statement indicating his Marxist beliefs, a confession said to run some 170 pages which the United States Central Intelligence Agency (CIA) will want to read, and yet another controversy about the British ability to safeguard secrets from the Soviets.

The CIA is directly affected. It routinely exchanges sensitive data with the British and other NATO allies, and it fears that its own information might find its way into Soviet hands.

The Thatcher government shares the US concern. The prime minister herself is said to be increasingly exasperated at the paradox of leaks from and secrecy within British secret services.

It was she who decided that Bettaney would be prosecuted through the courts - the first MI5 agent in history to be punished in public.

In part this was to show her allies that he had been caught before doing much damage, as Corporal Aldridge was, and that she was prepared to be tough.

After the trial she moved again, this time to launch a formal investigation by the Security Commission - the body that investigated the Rhona Ritchie, Aldridge, and Prime cases.

After the Prime case, in 1982, Mrs. Thatcher accepted a commission recommendation that lie detector tests be given to employees at the Cheltenham facility. Trade unions and others doubt the tests can trick spies who are determined to evade them. The first tests, however, are believed to have already taken place.

The Security Commission, set up in 1964, investigates security breaches at the request of the prime minister of the day and advises on changes needed.

It is headed by Lord Bridge, a judge in Britain's top court of appeal. Its four members are selected for each probe from a pool of public figures.

Despite US and other criticisms, Mrs. Thatcher is opposed to any change in the way secret services are vetted. Critics including the Guardian newspaper say elected members of Parliament should sit on a House of Commons select committee, just as senators and representatives sit on the Joint Intelligence Committee in Washington.

Mrs. Thatcher is now under rising pressure to make changes within MI5 - which operates on British soil - and MI6, which operates abroad.

The CIA will want to know why a man like Bettaney was ever allowed to head the counterespionage unit of MI5 in the first place. Lord Chief Justice Lane called him in court ''puerile, self-opinionated, and dangerous.''

Information leaked to British reporters after the trial indicated that, when recruited from Oxford University in 1975, Bettaney was an ultraconservative who had read widely on Nazism and Adolf Hitler.

By the end of 1982, undetected by colleagues or by supposedly regular security checks, he had reportedly become an active Marxist. He had filled his home with Russian icons and Russian music.

Like Guy Burgess before him, he is said to have been arrested for drunkenness in public, saying over and over again, ''I am a spy, I am a spy.'' A short while later, in 1982, he was allegedly back in court for failing to pay a railroad fare. Both cases were quashed by MI5.

Not only was no action taken against Bettaney, the leaked information alleged , but he was promoted to the key counterespionage job only a few months later, at the end of 1982.

He is said to have known details of all suspected Soviet agents in Britain, and of British agents working against them, and to have tried to offer some of this to a Soviet diplomat.

The Russians didn't react, however, and Bettaney was arrested before leaving for Vienna to try again.