Tom Driberg and Raymond Fletcher, who are both now dead, were listed as KGB agents in the files smuggled to the UK by former Soviet agent Vasili Mitrokhin.

The details of how the two MPs were recruited by Moscow's secret service are contained in a book, The Mitrokhin Archive: The KGB and The West, by Cambridge academic Christopher Andrew.

Raymond Fletcher: Died in 1991

Mr Driberg, who was MP for Barking, East London, was codenamed Lepage, while Mr Fletcher, then MP for Ilkeston, Derbyshire, was codenamed Peter, Mr Andrew said.

This latest disclosure follows the revelation that 87-year-old great-grandmother Melita Norwood passed secrets to the KGB for more than 40 years.

Former police officer John Symonds has also admitted being a "Romeo agent", who tried to get secrets for the KGB by sleeping with women from foreign embassies in the 1970s.

Mr Andrew said the two former MPs appeared prominently in the KGB files, which were brought to Britain by Mr Mitrokhin in 1992.

Vasili Mitrokhin: Left Russia in 1992

But Mr Andrew said: "Driberg's file shows that he was agent Lepage.

"He was one of many victims of the KGB's sexual entrapment."

Mr Fletcher, a part-time journalist who died in 1991, was identified as agent Peter, Mr Andrew said.

The latest details to emerge from the Mitrokhin files were predicted to be the first in a long line of cases waiting to be exposed.

Mr Andrew said the British material was only a small part of the whole material Mr Mitrokhin had smuggled out of Russia.

Files on SVR

He said that they even included secrets on the current head of the Russian intelligence service, the SVR.

Mr Andrew said: "Some of his secrets are in Mitrokhin files. His predecessor of Russian foreign intelligence, Yevgeny Primakov, also has secrets in the file."

Mr Mitrokhin, 77, is now living in fear of his life in a closely guarded house under an assumed name as he feared assassination.

Mr Andrew said he did not believe there would not be enough evidence to prosecute those who had been named as a result of the book, because there were no original copies of the files.