Mumbai: US authorities have secured a court order to seek information from UBS, Switzerland's largest bank, on US taxpayers suspected to be avoiding income taxes.

The order, issued by a US district judge in Miami, allows the US Internal Revenue Service to serve a summons on UBS to obtain information on possible fraud by people with unestablished identities.

The order by Judge Joan Lenard, issued on a justice department request for bank records, puts further pressure on Switzerland's secretive banks to open up. The court ordered that UBS hand over the names of as many as 20,000 of its US customers.

The probe followed last month's revelations by a former UBS banker, Bradley Birkenfeld, that he helped defraud the IRS by assisting UBS clients in avoiding US reporting requirements on income in Swiss bank accounts.

UBS employees helped wealthy US clients to conceal their ownership of assets held offshore by creating bogus entities and then filing IRS forms falsely claiming the entities owned the accounts, Bireknfeld told the court while pleading guilty.

Birkenfeld also revealed that he even helped a client by purchasing diamonds with the client's Swiss bank account funds and then smuggling them into the US inside a toothpaste tube.

UBS had about $20 billion of assets under management in "undeclared" accounts for US taxpayers, according to Birkenfeld.

As part of the IRS investigations, the justice department has now sought records of services provided by UBS to US clients from 2000 to 2007.

UBS, under pressure to overhaul its business after reporting more than $37 billion in writedowns during the global credit turmoil, on Tuesday, announced that four of its board members were stepping down later this year.

The court order will help IRS summon information about US taxpayers who have UBS bank accounts but did not file forms detailing their taxable income.

UBS said it was ''working diligently with both Swiss and US government authorities, consistent with Swiss law and the legal frameworks for intergovernmental cooperation and assistance".

While the US administration is yet to seek cooperation from Swiss authorities, Switzerland does not regard tax evasion as a criminal offence.

A Swiss parliamentary commission is weighing only the possible effects of the case for Switzerland as a financial centre while the Swiss banks and the finance ministry seem even less concerned.

The IRS, meanwhile, is seeking help from the world's top accounting firms such as Ernst & Young, PricewaterhouseCoopers, Deloitte & Touche, Grant Thornton, KPMG and BDO Seidman to broaden its campaign against tax evaders.
 
Tax dodgers are believed to cause hundreds of millions of dollars a year in lost revenues to the US government.