The foreign ministry summoned the German ambassador on Tuesday to tell him of Swiss anger at recent remarks by Germany's finance minister.
Peer Steinbrück had said that there were reasons to doubt promises by Switzerland and Austria to fully apply transparency standards prescribed by the Organisation for Economic Co-operation and Development (OECD). He singled out conditions being set out for sharing customer data, which he said would "maintain banking secrecy in principle".
"In my opinion, these statements are unacceptable, being contemptuous and aggressive both in substance and in form," Foreign Minister Micheline Calmy-Rey told parliament on Monday.
"I would have expected another reaction from Germany towards a partner like Switzerland, especially from a country that benefits from its relationship with Switzerland. Just think about migration, borders or even the trade balance."
The ambassador, Alex Berg, said he had take note of Switzerland's concerns during the meeting with the state secretary for foreign affairs, Michael Ambühl, on Tuesday.
Berg said the pair had a "very open" discussion, during which he had pointed out that Germany was not the only country concerned about the issue of banking secrecy.
The ambassador was last summoned in October when Steinbrück called for Switzerland to be blacklisted by the OECD as an uncooperative tax haven.