Prosecutors in the United States have accused three Swiss bankers of helping rich Americans to hide $1.2bn (€0.9bn) from the tax authorities.
Bankers Michael Berlinka, Urs Frei and Roger Keller were accused of "conspiring with US taxpayers and others" in a massive tax fraud scheme.
In an indictment, the three bankers were said to have been client advisers at the Zurich branch of an institution identified only as "Swiss Bank A".
They allegedly conspired with their US clients to hide the existence of bank accounts and the income they generated from the Internal Revenue Service.
The IRS collects taxes and requires US citizens to declare their holdings both at home and abroad.
Swiss banks have come under steady attack by US authorities, highlighted by a probe into banking giant UBS, which led to a deal between US and Swiss authorities.
The service by "Bank A" was allegedly ramped up in 2008 and 2009 "in an effort to capture business lost by UBS AG and another large international Swiss bank in the wake of widespread news reports that the IRS was investigating UBS for helping US taxpayers evade taxes and hide assets in Swiss bank accounts," New York federal prosecutors said in a statement.
They "allegedly told various US taxpayer-clients that their undeclared accounts at Swiss Bank A would not be disclosed to the United States authorities because Swiss Bank A had a long tradition of bank secrecy".
The three accused bankers live in Switzerland. If convicted in the US they would face a maximum term of five years in prison.
In the UBS case, some 4,000 case files on American clients of UBS were handed over to the US in 2010, after Washington dropped a summons against the bank over tax evasion.
US tax authorities had started their offensive against UBS in 2008 after questioning a former banker, prosecuting the bank through US courts and forcing it to pay a $780m fine and hand over client names.
