BERLIN (AP) — A Swiss man has confessed to a Frankfurt court that he spied for his country on German tax investigators in a case that has sparked tension between the two nations.

The dpa news agency reported Thursday the 54-year-old, identified only as Daniel M. according to privacy rules, told the court he received 28,000 euros ($33,000) from the Swiss NDB spy agency to obtain information on tax officials in the German state of North Rhine-Westphalia between July 2011 and February 2015.

Pleas aren't entered in the German trial system, but confessions are common and could mitigate a sentence.

The man is alleged to have been tasked with identifying German tax investigators who obtained a data CD containing confidential Swiss bank client data, and used it to open multiple tax evasion prosecutions.