LONDON (AP) _ A British Cabinet minister called an urgent meeting with the head of Britain's spy agency to determine why a great-grandmother, who once spied on Britain for the Soviet Union, was never prosecuted.

Home Secretary Jack Straw was expected to receive a full report today from Stephen Lander, head of the MI5 intelligence agency, as Prime Minister Tony Blair's Labor government came under increasing pressure to prosecute the 87-year-old woman.

News reports alleged the spy agency kept the government in the dark for years after finding out that Melita Norwood had been spying for the Kremlin.

Mrs. Norwood, a former secretary at British Non-Ferrous Metal Research Association, handed over Britain's atomic secrets to the Soviet Union, news reports said. She began spying in 1937 and continued until her retirement in 1972, they said.

``Many spies have been jailed for up to 40 years,'' said Ann Widdecombe, of the opposition Conservative Party, which led calls for Mrs. Norwood to face the courts. ``It seems inexplicable that a handful of people are going to get away with it.''

On Saturday, Mrs. Norwood _ now a frail figure with wispy gray hair _ read a statement in her suburban London garden saying she had no regrets and would do it all again.

``I did what I did, not to make money, but to help prevent the defeat of a new system which had at great cost given ordinary people food and fares which they could afford, good education and a health service,'' she said.

Her work as a spy was revealed in copies of thousands of KGB documents brought out of the Soviet Union by Vasili Mitrokhin, an archivist for the Soviet intelligence service who defected to the West in 1992.

The documents are the backbone of a book, to be published later this month, by Cambridge historian Christopher Andrew. Titled ``The Mitrokhin Archive,'' the book is being serialized by The Times of London.

The newspaper said Monday that Mitrokhin, 77, now a British citizen, is living under a false name with round-the-clock protection.

Mitrokhin fears reprisal from Russia because of his treachery in smuggling out the documents, which may unmask further spies, The Times said.

A second Briton, former policeman John Symonds, was also revealed in the documents. Symonds, now 64, said the Soviets trained him to be a so-called ``Romeo agent'' who seduced women working at Western embassies into revealing secret information.

``I was taught how to be a better lover, or perhaps I wasn't a very good one before,'' he said in a British Broadcasting Corp. documentary, to be broadcast on Sept. 19. Excerpts were screened Sunday.

Symonds, who was wanted on corruption charges when he fled Britain in the 1970s, told the BBC he was recruited in Morocco and carried out regular undercover missions for the KGB between 1972 and 1980.

News reports said he returned to Britain in 1980, gave himself up and served a two-year sentence on corruption charges. Symonds first confessed his spying in an interview with the Daily Express in January 1985.

Meanwhile, news reports said Britain's spy agency had identified Mrs. Norwood shortly after Mitrokhin fled Russia, but failed to inform government officials until this summer. No explanation was given for the delay.

``The Mitrokhin Archive'' makes other, wide-ranging claims of Cold War Soviet espionage, The Sunday Times and CBS' 60 Minutes reported, including that the KGB planted rumors that the CIA assassinated President John F. Kennedy.

The newspaper and 60 minutes also reported that booby-trapped explosives were hidden across the United States and Europe to target pipelines, railways, oil refineries and electrical stations. The Times, the sister paper of The Sunday Times, said records of the exact locations have disappeared.

A KGB plan to disrupt the investiture of Prince Charles as the prince of Wales in 1969 was also disclosed. But the scheme was later aborted, according to The Times.