Vic Allen, a former lecturer in trade union studies at Leeds University and one time confidant of the miners' leader, Arthur Scargill, has admitted passing on secrets to the East Germans.
Gwynneth Edwards, who taught at Loughborough University, is also identified as an agent in Stasi files, which have been obtained by the UK security services. The disclosures take the number of living Britons to have been accused of spying in the past week to five.
The existence of the Stasi ring has been exposed by American intelligence officers who have now handed all their information to the British secret services.
It focused on Dr Robin Pearson, a senior lecturer in economic and social history at Hull University, who is said to have worked for the East German secret police for 12 years.
Professor Allen, 77, who has never made any secret of his pro-Soviet sympathies, admits that he provided information to East Germany but denies betraying his country, acting illegally or receiving any payment. "It was perfectly legitimate that I should do that," he says in the BBC2 documentary series, The Spying Game, broadcast next month. "I have no shame. I feel no regrets."
Dr Edwards, a modern languages expert, has been identified by the East German spec- ialist Professor David Childs, who has had access to the East German secret police documents. Last night he confirmed that she was named in the files.
"The East Germans liked to recruit foreign academics because they often had access to research information. They could get into government service or spy on other academics."
Dr Edwards is alleged to have been part of a 20-strong spy ring recruited by the East Germans. It is said that one of her roles was to report back to her controllers on any anti-Communist comments made by visiting German academics. It was not possible to contact her last night.
Dr Pearson, codenamed "Armin", was allegedly recruited while studying in Leipzig as part of his German history degree at Edinburgh University. A Home Office spokesman said yesterday that he had been interviewed by the security services in 1994 but it was decided that there was "no usable evidence" against him. His Stasi handler, Berhart Kartheus, told the BBC that the East Germans successfully recruited one in 10 of the British exchange students they approached during the Cold War. Experts estimate that this means there are likely to be up to 20 still living in the UK.
A massive undercover investigation is now under way by MI5 and MI6, Britain's internal and external security services, to track down and prosecute up to 30 Britons suspected of handing secrets to the Eastern bloc before the fall of the Berlin Wall. They are thought to include serving police officers, who have been identified by the former Scotland Yard detective and the self-confessed agent, John Symonds.
The operation will fuel Opposition criticism of the Government's decision not to prosecute other agents recently unmasked, including the great- grandmother, Melita Norwood.
Up to 15 former KGB agents are also under investigation in a separate operation after being identified from the files brought out of Russia by the defector Colonel Vasili Mitrokhin. Their names were deliberately withheld from the published version of his archive in order to stop them fleeing the country to escape prosecution. British intelligence officers are now interviewing other KGB defectors in an attempt to build up a case that will allow charges to be brought successfully.
Ann Widdecombe, shadow home secretary, demanded a full explanation from the Home Secretary, Jack Straw about the Government's failure to prosecute the alleged agents.
The Home Office issued a statement saying it would be impossible to disclose all details of security service investigations. "In fulfilling its function of protecting national security, the Security Service has ... carried out a great many investigations, including into alle- gations of espionage and hostile foreign intelligence activity.
"It is wholly unrealistic to believe that the detail of [investi-gations] should routinely be made public. It would be grossly irresponsible, as disclosure could seriously compromise the work of the agencies which, to be effective, have, to a large degree, to remain secret."