U.S. wants names of 52,000 customers of Swiss bank UBS

— -- Federal authorities have filed a lawsuit against Swiss-based bank UBS, seeking the identities of up to 52,000 U.S. customers.

The suit filed in Miami Thursday seeks to force the firm to turn over information on customers who hid their accounts from the U.S. government in violation of tax laws.

According to U.S. officials, an acquisition in 2000 of a U.S. company brought UBS a host of new American clients. The bank then set about evading new reporting requirements for those clients. To do so, UBS executives helped U.S. taxpayers open accounts in the names of sham entities.

Prosecutors contend that UBS executives used encrypted software and other counter-surveillance techniques to prevent anyone from detecting that they were actively marketing such Swiss bank secrecy — and tax evasion — to American taxpayers.

The clients, in turn, filed false tax returns that omitted the income they earned in their Swiss accounts, according to the court papers.

According to the government's lawsuit, the accounts in question held about $14.8 billion in assets the past decade. UBS says it will fight in court to keep the names private, arguing Swiss bank secrecy laws shield those customers.

The suit comes a day after the Justice Department struck a deal with UBS to get access to some of its customers who used Swiss bank secrecy law to hide billions of dollars in assets.

After that settlement of a criminal case was announced, the bank's chairman, Peter Kurer, said in a statement the firm accepted "full responsibility" for helping its U.S. clients hide assets from the IRS. But that does not mean the bank is about to fork over information on thousands of accounts.

"This shows the big fight is yet to come," said George Clarke, a tax attorney based in Washington who is not involved in the UBS case.

On Wednesday, cracking Switzerland's historic reputation for banking secrecy, UBS agreed to a $780 million settlement of federal charges it helped about 19,000 wealthy American clients evade U.S. taxes and said it would disclose the identities of some of those customers.