German politicians were divided at the weekend over whether to buy the bank data of up to 1,500 possible tax evaders with accounts in Switzerland that media say an informant has offered to sell authorities.
The respected Frankfurter Allgemeine Zeitung reported that the whistleblower is asking for 2.5 million euros for the confidential data, which tax investigators believe could rake in 100 million euros for German state coffers.
The case risks prompting a fresh row over bank secrecy between Germany and Switzerland. Top Swiss politicians, including President Doris Leuthard, and bankers warned Germany against acquiring the data.
Without citing sources, Financial Times Deutschland reported in its online edition that the data belonged to German clients of HSBC
France already acquired some of that information last year by raiding the computer specialist's house, and used it to track down fraudsters, infuriating Switzerland.
A spokesman for the German Finance Ministry declined to comment on the report but said it would be the responsibility of individual German states to deal with such data.
A senior ally of Chancellor Angela Merkel, Defense Minister Karl-Theodor zu Guttenberg, said Germany would have to carefully check its legal right to purchase the alleged data.
I have a problem with handing over money for something that has come into someone's possession in a legally questionable fashion, Guttenberg told Swiss daily Neue Zuercher Zeitung.
Members of the opposition Greens and Social Democrats (SPD) however encouraged the government to buy the data on behalf of honest taxpayers.
Nicolette Kressl, SPD finance expert, told Die Welt am Sonntag the government should proceed as it did in 2008, when it purchased data on tax evaders from an informant about clients of a Liechtenstein bank.
The case snared former Deutsche Post chief Klaus Zumwinkel, who was given a suspended jail term for evading nearly a million euros in taxes using a Liechtenstein trust.
Former Finance Minister Peer Steinbrueck repeatedly accused Germany's neighbors Switzerland, Liechtenstein and Luxembourg of serving as havens for German tax evaders, but the three countries have taken steps in the last year to improve transparency on taxes amid a global crackdown on tax havens.
(Reporting by Sarah Marsh and Hans-Edzard Busemann in Berlin and Catherine Bosley in Zurich; writing by Sarah Marsh; editing by Andrew Roche)