Shares in embattled Swiss bank UBS fell to an all-time low on Monday, ending the day at SFr10 ($8.58) or 9.1 per cent lower than at Friday's close at the Swiss bourse.

The decline came as a federal judge decided it would take months to determine if and when the Internal Revenue Service (IRS) would gain access to accounts of 52,000 UBS clients in the US suspected of tax evasion.

District judge Alan S. Gold set a July 13 hearing on the IRS lawsuit, unless an agreement is reached first. He gave UBS until April 30 to prepare their defence.

UBS has argued that handing over the account names would violate Switzerland's banking secrecy legislation and jeopardise the bank's licence to stay in business.

"Such violations would expose these [UBS] employees to substantial prison terms, as well as fines, penalties and other sanctions," UBS lawyers said in a court filing.

The lawsuit seeking details of the 52,000 accounts containing an estimated $14.8 billion in assets was issued last week.

It came a day after Switzerland's largest financial institution came to a settlement with the Justice Department on revealing the names of up to 300 US customers and payment by the bank of $780 million.

Under the terms of the settlement, UBS admitted helping US taxpayers hide accounts from the US Internal Revenue Service, the agency responsible for tax collection and tax law enforcement.

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