The head of Germany's reformed communist party has been unmasked as a spy for the former East German secret police by researchers studying files that have been returned to Germany by the CIA.
A team of 50 analysts is going through the "Rosenholtz" (Rosewood) files - the last remaining record of East German espionage - which were taken to Washington during the final days of the GDR (German Democratic Republic) and returned earlier this month.
The files, whichcontain 320,000 agent cards and 57,000 spy reports, name Lothar Bisky, the chairman of the German Party of Democratic Socialism (PDS), as an "unofficial" Stasi informant. He is said to have worked under the codename "Bienitz" for the Stasi's foreign spy service, the HVA.
Recruited by the Stasi in 1966, he was taken off duty in 1979, only to be "reactivated" in 1986 when he became the director of the film and television school attached to the Babelsberg studios in Potsdam, west of Berlin, the files show. Although Mr Bisky has previously admitted contacts with the Stasi, he denied he was registered as an informant.
Hubertes Knabe, the director of Berlin's Stasi memorial centre, called on Mr Bisky to come clean about his espionage activities. "[German] citizens have a right to know whether and how politicians co-operated with state security services," he said.
The revelations have raised questions about the future of the PDS after its defeat in last September's national election. It nowhas two MPs in the Bundestag, the German parliament.
Mr Bisky, who emigrated to the GDR from West Germany in 1959 held posts in various international organisations enabling him to travel abroad. He has maintained the revelation is nothing new, saying he already dealt with the issue in 1995. "I confirmed having official contacts with the [GDR] state security in my work, right from the beginning," he said.
He now claims, however, that he never signed a document confirming he would spy for the GDR, an assertion that can never be proved as the files containing such documentation were destroyed as the East German regime crumbled in 1989.
Observers say it is difficult to see the PDS enjoying any sort of revival under a chairman who worked for HVA, but Mr Bisky says he will not resign.
The Rosewood files are expected to unmask up to 40,000 former East German spies.