US authorities Tuesday asked a federal court to order UBS to reveal the names of American offshore account holders, saying the Swiss bank "systematically and deliberately" violated US laws.
In a memorandum filed in US District Court in Miami, the Justice Department called for the enforcement of a summons stemming from a government lawsuit filed earlier this year.
The case affects as many as 52,000 US taxpayers suspected of holding offshore accounts managed by UBS to avoid paying taxes to the US government.
The memo said the Internal Revenue Service "seeks the identities of those account holders (and other account information) from a Swiss bank that regularly conducted business in secret within the United States, and systematically violated US law."
"Tens of millions of Americans report their income, obey the law, and pay their taxes, because it is the law and following the law is the obligation we take on as citizens and residents," the memo stated.
"The summons in this case will help the IRS ensure that those US taxpayers whom UBS assisted to avoid their US tax obligations will also obey the law. The United States has proven its case for enforcement."
In February, UBS admitted to US tax fraud and agreed to pay 780 million dollars as part of a provisional deal to settle charges by the US government that it helped thousands of American clients use Swiss accounts to evade US taxes.
But US officials have argued this was not enough, and asked for the identities of all such account holders.
The Swiss bank has argued releasing the names would violate bank secrecy laws in Switzerland.
US authorities countered meanwhile that "Swiss law, principles of international comity, and the QI (qualified intermediary) Agreement do not shield US taxpayers from liability, where UBS has systematically and deliberately violated the laws of the United States on US soil."
According to a UBS document filed with the lawsuit, as of the mid-2000s, those secret accounts held about 14.8 billion dollars in assets and the American clients had failed to pay taxes on income earned in those accounts.
US legislators have accused UBS and other banks of helping wealthy Americans hide about 1.5 trillion dollars in overseas tax havens.
According to the US lawsuit, Swiss-based bankers actively marketed UBS's services to wealthy American customers within the United States.
A trial in the case is set to open July 13. Some media reports had indicated the US government was prepared to drop the lawsuit in exchange for an out-of-court settlement.
