The woman, codenamed Hola by the Soviet secret service, allegedly passed highly sensitive atomic secrets to Stalin's regime for 40 years, allowing the Eastern bloc to accelerate its nuclear weapons programme.
The discovery was made by a Cambridge academic, Christopher Andrew, while researching thousands of archives smuggled from the former Soviet Union by dissident KGB officer Vasili Mitrokhin. The claims are made in Mr Andrew's new book, The Mitrokhin Archive.
Among the archives, which filled six trunks, were details of the British spy who leaked secrets with apparent impunity while she worked as a secretary in the British Non-Ferrous Metal Research Association, a body whose work was vital to the development of the British nuclear deterrent.
Last night, the Home Office declined to discuss the issue of whether Hola would be charged with treason. The Home Secretary is understood to have been informed by the intelligence services of Hola's former activities but it is believed he will take no action on account of her age, and in consideration of whether it would be in the public interest to do so.
But there were calls for Jack Straw to review that decision, with some opposition politicians claiming that the age of the offences - her first state secret was passed to the Soviets in 1937 - should be no bar to at least an investigation. The war crimes prosecution against Anthony Sawoniuk proceeded earlier this year despite the time since his murder of Jews in Eastern Europe during the Second World War.
Ann Widdecombe, the Tory home affairs spokeswoman, said:"It is beyond belief if Jack Straw has really known about this and said nothing. I would ask why there has been no public statement. You simply cannot overlook 40 years of treachery and if a prosecution is inappropriate there must still be a full exposure."