The US authorities are “holding up” a resolution of the tax dispute with Switzerland by making demands that the Swiss authorities find unacceptable, Swiss media are reporting.

The Swiss finance minister, Eveline Widmer-Schlumpf, told Zürcher Regionalzeitungen newspaper that, since the US and Switzerland agreed to take a comprehensive approach to the tax dispute, “new demands are constantly being made that we cannot accept.” The Swiss authorities later confirmed the comments to this publication. 

The US has requested information on former clients of Credit Suisse. "The demands on Credit Suisse are related to a request for administrative assistance in cases of tax fraud, based on the Swiss-US double taxation agreement of 1996," the Swiss Federal Department of Finance said in an emailed statement. 

This follows an attempt in April to gather such information, which was blocked by Swiss courts as it did not list clients' names specifically but instead gave "vaguer" criteria hinting at tax evasion, according to Reuters.

The authorities have been trying to reach a deal, as part of which the Swiss hope to get the US to drop individual investigations into 11 banks for allegedly aiding tax evasion, in exchange for fines and client names.

This follows from UBS’s settlement of criminal and civil charges with the US authorities in 2009, which saw the bank pay $780 million and transfer names of up to 4,450 US clients to the US authorities, a move that was seen at the time as a significant breach of Swiss bank secrecy law. The pressure on Switzerland is significant as the Alpine state generates about 12 per cent of its gross domestic product from banking and financial services.

Just recently, Sean Roberts and Nadia Roberts of Tehachapi, CA, were sentenced to 12 months and 1 day in prison for filing a false tax return related to undisclosed offshore bank accounts. Information relating to their account had been passed to the Internal Revenue Service as part of the UBS agreement.

In another move related to the long-running tax affair, the US has indicted Wegelin, in the first instance where it has accused a foreign bank, rather than individuals, of helping US citizens commit tax fraud. Wegelin was accused of helping clients hide more than $1.2 billion in offshore bank accounts. Following the accusations against it earlier this year, Wegelin & Co – founded in 1741 – broke up.

Widmer-Schlumpf could not say how long negotiations with the US would last, but said the Alpine state was holding firm on certain points and that any compromises had to work under Swiss law.

Credit Suisse had not replied to a request for confirmation at the time of going to press.