“We dealt with the case five years ago. The FIS submitted it to us at the time,” MP Corina Eichenberger, vice-president of a delegation that supervises the FIS, told news agency ATS on Wednesday.
On Friday German prosecutors said police had arrested a 54-year-old Swiss man identified only as Daniel M, who was suspected of espionage activities since early 2012.
German newspaper Die Welt reported that the man's alleged mission was to identify German tax investigators involved in the purchase of "tax cheat" CDs which list German citizens' account information with several Swiss and Liechtenstein banks.
“Germany carried out economic espionage in buying these CD-Roms containing banking data,” said Eichenberger.
The FIS then put the Swiss agent on a counter-espionage mission to find out who ordered the purchase of the CDs.
“On the back of his information, arrest warrants were issued for three German tax inspectors for alleged economic espionage,” said Eichenberger.
Counter-espionage is part of the intelligence service's remit and it was carried out within the law, she added.
“If we didn't think so we would have intervened and at least rebuked the FIS for its actions”.
Eichenberger added that she didn't think the spy's arrest was related to his activities five years ago but was “probably something different”.
On Tuesday Berlin summoned the Swiss ambassador to clarify the situation.