The UBS bank has confirmed it handed over sensitive data about its competitors to United States investigators.

The documents contained information about which institutions had taken over UBS clients when the justice authorities clamped down on the bank in 2009 after it admitted helping wealthy Americans hide money to avoid paying tax.

The report was carried in Thursday’s Handelszeitung economic weekly and confirmed by UBS.

The weekly says the US authorities, who are now investigating a number of other Swiss banks, including Wegelin, Julius Bär and the Basel cantonal bank, were tipped off by these documents, rather than by taxpayers coming clean in order to avoid larger penalties.

A UBS spokesman told the Swiss News Agency that the bank had been obliged to hand over the information as part of the mutual judicial assistance procedure.

He added that it had followed the instructions of the Swiss authorities.

The documents it had been ordered to hand over included customer correspondence and instructions for closing their accounts, he said.

Representatives of the Wegelin bank have been summoned to appear in a New York court on Friday to answer charges in connection with aiding US citizens to hide their assets in order to escape tax.

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