The agreement reached by the US and Liechtenstein governments will put pressure on the Switzerland government to forge a similar pact, which could in-turn accelerate the UBS tax evasion investigation, according to US tax attorneys.

Liechtenstein said it would grant US tax authorities access to information kept by its banks on US citizens in certain cases of tax evasion, effectively ending the distinction between tax fraud and tax evasion in the country.

Neighbouring offshore giant Switzerland has not agreed to a similar agreement, but could now be under pressure to make a pact with the US government, said Manhattan based attorney and Rubinstein & Rubinstein partner, Asher Rubinstein.

The US Department of Justice and the Internal Revenue Services are currently investigating whether certain US clients sought to evade their US tax obligations with the assistance of UBS client advisors as part of an ongoing investigation.

Press reports have recently included Credit Suisse and HSBC in the same investigation.

If Switzerland signs an agreement similar to the Liechtenstein agreement, the US government is likely to come closer to prosecuting people currently in their sights for avoiding US taxes.

“The basis of the Liechtenstein pact is the US can request information for specific people – they can’t just go on a fishing expedition and ask for the names of all US taxpayers who have offshore bank accounts – they need to have predetermined people they are interested in,” Mr Rubinstein said.

“There is no doubt this agreement now puts the pressure on the Swiss government to do the same,” he added.

UBS is said to have handed on a “small group” of names who were clients with the firm’s now defunct US cross-border business that were likely to be of “potential interest” to US authorities as part of their ongoing investigation, people close to the firm have said.

UBS could not offer up its clients' information to US authorities without breaching Swiss law, even though US authorities requested the information, a UBS spokeswoman confirmed.

“Under Swiss law, UBS cannot turn over Swiss-based client data to US – or other foreign government – authorities,” the spokeswoman said.

“Pursuant to a Switzerland-US treaty, such matters must go through an ‘administrative assistance’ process. The administrative assistance proceedings are a matter between the relevant domestic and foreign authorities and the UBS clients concerned,” UBS said in a statement to WealthBriefing.

Peter Hardy, a partner with Philadelphia based law firm Post & Schell who represents UBS clients in the matter, estimates there are “several dozen” US attorneys representing the interests of individuals who held accounts with UBS’ cross boarder business.

“There is no lawyer I know who will counsel their client to do an evasive act, but by liquidating their accounts, UBS has put these people in a bad position, even those with the desire to come clean,” Mr Hardy said.

In August UBS sent a letter to its clients US offshore-banking clients advising them to respond within 45 days to discuss the transfer of their account holdings.