Switzerland's tax battle with Germany has escalated anew: the alpine nation is bringing charges against three Germans over so-called cum-ex products sold by private bank J. Safra Sarasin.

Zurich prosecutors have charged three Germans with industrial espionage and violating banking secrecy, news agency «Reuters» reported on Monday. A Stuttgart lawyer as well as two former Swiss bank employees are in focus, according to various media including German weekly «Die Zeit», German broadcaster «ZDF» and Swiss online outlet «Republik».

The trio are accused of handing over confidential client data to German officials – which they deny. If convicted, they face sentences of up to three years in jail.

The most recent escalation of a long-brewing tax fight between the two countries has its roots in a legal battle between Swiss-Brazilian private bank J. Safra Sarasin and German millionaire Erwin Mueller. The drug store mogul lost money on questionable tax-savings products called cum-ex funds, as finews.com previously reported.

Drugstore Mogul's Fight

Last year, Safra Sarasin was ordered to pay Mueller 45 million euros in damages, which the bank is appealing. His lawyers reportedly received confidential bank document which were submitted as evidence in that lawsuit, and later handed over to German authorities. 

Last autumn, a former UBS security staffer admitted to spying on German tax investigators for Switzerland, an affair which ratcheted up tension between the two countries which share a border. The move by Zurich's prosecutors represents another chapter in the tit-for-tat saga.