THE UNITED States is building criminal cases against more than 150 American clients of Swiss bank UBS as part of a crackdown on tax evasion now made easier by a deal over access to secret account information.

US prosecutors gave their first official confirmation of the initial number of criminal investigations in a filing yesterday with a federal court in Fort Lauderdale in Florida.

In the same court document the prosecutors requested a sharply reduced prison sentence for ex-UBS banker Bradley Birkenfeld, a key informant in the ongoing US prosecutions of wealthy American clients of UBS.

The request was made a day before US and Swiss authorities were due to announce details of a negotiated settlement of their legal dispute over access to further names of UBS clients suspected of cheating US tax collectors.

In the court filing prosecutors said evidence provided by Birkenfeld had been critical in obtaining information from UBS that directly led to the investigations into the more than 150 Americans “who are believed to have concealed income and assets at UBS” from US tax authorities.

Citing the settlement, due to be finalised today, the filing said: “It is expected that . . . UBS will produce the identities and account information of additional UBS customers who are believed to have violated United States law.”

A US legal source told Reuters on Monday that UBS, the world’s second-largest money manager, was expected to give US authorities the names of about 5,000 more Americans suspected of using the Swiss bank to evade taxes.

The deal was agreed last week to end a dispute in which US tax authorities originally asked for details on 52,000 clients suspected of tax evasion, triggering fears in Switzerland about the impact on the country’s laws on bank secrecy.

In the court filing, prosecutors said Birkenfeld, a US citizen who will be sentenced on Friday, had faced up to five years’ imprisonment after pleading guilty in June 2008 to helping a US billionaire hide $200 million in assets from US tax authorities.

The prosecutors asked that Birkenfeld’s sentence be reduced to 2½ years’ imprisonment, citing his co-operation in efforts to uncover what they called a “multibillion dollar scheme to defraud the United States”.

UBS first became the target of US probes in 2007 when Birkenfeld first began co-operating with US authorities and helped them start building criminal and civil complaints against the bank and its customers. – (Reuters)