Germany's former foreign minister and senior Social Democrat Frank-Walter Steinmeier has became the latest German politician to face allegations of academic plagiarism, an act which brought down two of Angela Merkel's ministers.
Weekly magazine Focus cited university professor Uwe Kamenz as saying that he had found 500 areas of suspicious "similarities" when comparing Steinmeier's doctoral thesis in law in 1991 with some 100 sources.
Steinmeier, who heads the Social Democrats' (SPD) parliamentary group and will be one of six party leaders to head talks with Merkel's conservatives over a possible grand coalition, described the allegations as absurd, according to the magazine.
He said would be open to a review of the thesis by his former university.
Neither Kamenz nor Steinmeier could be contacted immediately by Reuters.
Merkel ally Annette Schavan resigned in February from her post as education minister, after being stripped of her doctorate by Duesseldorf University, which ruled she had "systematically and intentionally" copied parts of her thesis more than 30 years before.
Two years earlier, Karl-Theodor zu Guttenberg resigned as defence minister after being exposed for plagiarising his thesis - behaviour that Schavan condemned at the time as 'shameful'.
Other German politicians have also lost their academic titles as a group of anonymous Internet activists took to examining doctoral dissertations on websites in search of plagiarism.