A class action lawsuit has been filed in the United States against UBS by shareholders angry at the loss of the bank's stock as a result of a tax fraud probe.

The shareholders say they were duped into investing in Switzerland's biggest bank, which failed to disclose that its strategy to attract "net new money" was accomplished through a fraudulent scheme.

This involved helping wealthy investors evade federal taxes by placing money in undeclared Swiss bank accounts.

The lawsuit was first filed on January 30 by investors who bought UBS securities between May 4, 2004 and January 29, 2009, it emerged on Friday.

UBS shares climbed by more than 80 per cent on the Swiss stock exchange between 2004 and 2007 but fell by around the same amount between April 2007 and January 2009.

A line was drawn under another UBS concern on Thursday after the Federal Tax Administration announced that the US had withdrawn a request for administrative assistance from Switzerland in its probe into tax fraud at the bank.

The request was related to a criminal case, which was settled after UBS agreed to identify certain US clients and pay a $780 million (SFr875 million) fine.

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