(Bloomberg) A former banker at a Credit Suisse Group AG unit pleaded guilty to helping American clients evade taxes, increasing pressure on the bank amid a U.S. probe of how it helped wealthy Americans cheat the Internal Revenue Service.

Andreas Bachmann, 56, a Swiss citizen, pleaded guilty today in federal court in Alexandria, Virginia, where he and six other Credit Suisse bankers were indicted in 2011 on a charge that they helped U.S. clients hide $4 billion in assets from the IRS.

U.S. District Judge Gerald Lee reviewed Bachmann’s plea bargain in court and said the banker agreed to cooperate with U.S. prosecutors. The judge set sentencing set for Aug. 8. Bachmann faces as long as 46 months in prison under the agreement.

Credit Suisse is the largest of 14 Swiss banks under U.S. criminal investigation in a crackdown on offshore tax evasion. Bachmann’s plea follows a report by the Senate Permanent Subcommittee on Investigations saying Credit Suisse helped 22,000 Americans hide as much as $10 billion from the IRS.

Chief Executive Officer Brady Dougan apologized to the panel at a Feb. 26 hearing, saying a small group of Swiss-based bankers appear to have broken U.S. law and fooled top managers.

He said bankers worked with outside intermediaries to help U.S. clients set up offshore shell entities with money deposited at Credit Suisse in the names of the entities rather than the clients. Such conduct, Dougan said, was egregious.

‘Unlicensed’ Advice
Bachmann was “a private banker and asset manager who provided unlicensed and unregistered banking services and investment advice to U.S. customers who maintained undeclared accounts at banks in Switzerland,” according to an indictment in which he was accused of conspiracy to violate U.S. tax law.

Bachmann worked from “in or around the 1990s to in or around 2007” at a wholly owned subsidiary of the bank, according to the indictment. From 2007 to 2009, he worked for a Zurich-based asset management firm, then joined several other partners in July 2009 to form another asset management firm in Zurich, according to the indictment.

Calvin Mitchell, a Credit Suisse spokesman, said in an e-mail that Bachmann was an employee of Credit Suisse Fides until 2006. Mitchell declined to comment further.

The case is U.S. v. Walder, 11-cr-00095, U.S. District Court, Eastern District of Virginia (Alexandria).