The green light has been given to the US Internal Revenue Service to request the names of clients who may have been using Swiss bank accounts to evade federal income taxes, following a federal court order yesterday.

The order, made late in the afternoon US Eastern Standard Time in the Federal District Court in Miami, authorised the IRS to issue a civil summons to UBS to obtain the names.

The order followed a guilty plea by former UBS banker Bradley Birkenfeld on 19 June for conspiring to defraud the IRS by assisting UBS clients to avoid US reporting requirements on income in Swiss bank accounts. According to Mr Birkenfeld’s court statement, UBS had approximately $20 billion of assets under management in "undeclared" accounts for US taxpayers.

A statement from UBS obtained by WealthBriefing said: "We are aware that District Court of Southern Florida has granted the IRS permission to issue a civil summons directed to UBS AG.”

The UBS statement continued: “UBS looks forward to working with the IRS to address the summons.”

It continued: “As we have noted, UBS takes this matter very seriously and is working diligently with both Swiss and US government authorities, consistent with Swiss law and the legal frameworks for intergovernmental cooperation and assistance.”

The court ruling comes a day after the US Justice Department filed papers seeking the order.

The order was signed by U.S. District Court Judge Joan Lenard and authorises the IRS to serve what is known as a "John Doe" – a summons to obtain information about possible tax fraud by people whose identities are unknown.

The summons, approved by the court, directs UBS to produce records identifying US taxpayers with accounts at UBS in Switzerland who elected to have their accounts remain hidden from the IRS. The request covers accounts that were monitored as well as managed by UBS. The forms report income earned or taxes withheld.

According to the Department of Justice, the law requires a US taxpayer to report all financial accounts in a foreign country if the total value of the accounts exceeds $10,000 at any time during the calendar year. A willful failure to report a foreign account can result in a penalty of up to 50 per cent of the amount in the account at the time of the violation, a Justice department statement said.

In a statement issued yesterday, the IRS commissioner, Douglas Shulman, said that the agency would "pursue people and advisors identified through the summons process who use offshore bank and financial accounts to circumvent their tax responsibilities." He said that the process was "part of the overall IRS effort to stop offshore tax evasion."