The former lawyer, Kenneth Heller, banked the money with UBS and then moved it to a smaller private Swiss bank Wegelin in June 2008 after reading that UBS might identify account holders, federal prosecutors were reported to have said.

Heller, 81, is the sixth person to plead guilty to criminal charges of tax evasion out of seven charged in April 2010. He faces a possible maximum prison term of 15 years after his guilty plea in the US District Court in Manhattan. Sentencing was scheduled for 27 September.

In February 2009, UBS entered into a deferred prosecution agreement with US authorities, admitting it had helped taxpayers hide accounts from the Internal Revenue Service. UBS has agreed to pay a $780 million fine. Under this criminal case, UBS has provided the government with names and accounts of some individuals; in a separate, civil case agreed later in 2009 between the US and Switzerland, UBS is handing over thousands more account details. The development was seen as a historic breach of Switzerland’s centuries-old bank secrecy laws.

The indictment against Heller said he had opened a UBS account in the name of a sham offshore company in December 2005. The next month, he wired $26.4 million from the US to the account and his name did not appear as the account holder on UBS documents, reports said.