The allegations are partly based on information from Brandt's widow, Brigitte Seebacher-Brandt. Ms Seebacher-Brandt has, since her husband's death in 1992, fallen out with almost all the current leaders of the Social Democrats (SPD), including Rudolf Scharping, the party's candidate for Chancellor in this year's elections. Ms Seebacher-Brandt, meanwhile, has been conspicuously flirting with the political right.
Brandt, who was Chancellor in the early 1970s, remains a hero for most Social Democrats and is still spoken of in reverent tones even by Christian Democrats. He is seen as the embodiment of both the vision and the conscience of post-war Germany. Direct attacks on Brandt are still almost unthinkable, but he and his party can still be damaged by association.
Documents published recently in Der Spiegel magazine suggest that Herbert Wehner, a former Communist and parliamentary floor-leader of the SPD under Brandt, collaborated with the KGB during the time he spent in Moscow in the Hitler years.
In addition, and more obviously damaging, information supplied by Ms Seebacher-Brandt to the conservative Frankfurter Allgemeine Zeitung suggested this week that Wehner had conspired with the Stasi to engineer Brandt's fall. Brandt was forced to resign in 1974 after Gunter Guillaume, one of his aides, was arrested as a Stasi spy. The Frankfurter Allgemeine talked this week of Wehner having 'done the work of the other side'.
There have also been allegations against Karl Wienand, another senior figure in the SPD in the early 1970s, who, Ms Seebacher-Brandt suggested to the Frankfurter Allgemeine, had also worked for the KGB. She claimed that the former Soviet ambassador, Valentin Falin, had told Brandt of the KGB link in 1992, though Mr Falin has denied it.
According to different sets of accusations, the Stasi helped Brandt to survive a vote of no confidence, and later helped, through Wehner, to get rid of him. Conspiracy theories, in other words, abound.
All of the swirling and contradictory allegations have shed little light, but have conspicuously soured the tone of the political debate. In a front-page commentary headlined 'The Black Widow', this week's Die Woche noted: 'No question: the election campaign has begun,' and complained of 'campaign journalism' and the 'revival of old enemies'. Die Woche suggested that the revelations about Wehner, the now dead Communist-turned-Social Democrat, 'may be important for historians, but will not interest the voter'.
Some argue that the revelations may partly represent the settling of old scores. Ms Seebacher-Brandt is embroiled in a fierce battle to prevent her husband's papers from staying with the SPD-friendly Friedrich Ebert Foundation; the dispute seems set to end in court, to the fury of the SPD. In the words of the headline in Die Zeit this week, Ms Seebacher-Brandt is an 'heiress on the warpath'.
Die Zeit argues that Ms Seebacher-Brandt is, in a sense, fighting against her own husband, with her frequent insistence on re-interpreting what he 'really' meant, including his Ostpolitik, the policy of opening up to Germany's eastern neighbours, regarded by many as as Brandt's greatest achievement.
In the words of Die Zeit, 'she wants the truth to come out - her truth. Including the truth about Ostpolitik, which he believed was the great success of his life, but which for her was not anti-Communist and not German enough. She believes that all of this must come out, even if it means burying Brandt for a second time.'Reuse content