''If Germany buys stolen bank data, we'll push for a legislative change that would have to disclose all Swiss accounts of German people who hold public office,'' MP Alfred Heer of the right-wing Swiss People's Party told daily Bild.
He said information from Swiss banking circles indicated that German politicians, officials and judges had offshore account in Switzerland and Liechtenstein designed to avoid tax.
''The first such information has already been offered to us,'' he said.
Germany has angered Switzerland by agreeing to purchase a stolen disc containing the names of 1,500 Swiss account holders who may have defrauded the German taxman.
German Finance Minister Wolfgang Schäuble said at the beginning of this month that Germany would stump up a reported €2.5 million to an anonymous whistle-blower for the disc.
Since then the German state of Baden-Wuerttemberg said it had been offered a second disc containing 2,000 names. According to the Frankfurter Runschau daily it includes data from Swiss banking giants UBS and Credit Suisse as well as insurer Generali.
Schäuble told Saturday's Frankfurter Rundschau that he backed the purchase
of such data, saying, "My sympathy for people who regularly defraud the tax authorities by putting their fortunes in other countries is limited."
The daily also reported that an unidentified German multimillionaire had taken legal action against the German subsidiary of UBS, accusing it of encouraging him to evade tax.