The US Justice Department indicted a Swiss banker Thursday for helping US taxpayers hide millions of dollars in assets in offshore accounts over nearly two decades to avoid paying taxes.

The department said that Martin Dunki, working for the small bank Rahn & Bodmer Co., continued to help clients hide money even after the US government fined Swiss bank UBS $780 million in 2009 for doing the same.

Beginning in 1995 Dunki helped US clients place money in accounts of foundations and foreign-based companies not linked to the on paper, the indictment said.

After the US authorities began cracking down on tax avoidance, in 2009 Dunki and co-conspirators took the money from clients' accounts and used it to buy gold and other precious metals which were transferred to escrow accounts in his bank, according to the indictment.

Then the assets were moved to a vault in UBS for safekeeping. Dunki later travelled to the United States to report to the clients on their assets.

He also helped repatriate funds to the clients in ways that would prevent US officials from discovering the undeclared accounts, the indictment said.

The indictment named Zurich lawyer Edgar Paltzer as one of the co-conspirators.

"Martin Dunki went to great lengths to help his US taxpayer clients secret away millions of dollars in Swiss bank accounts," said Preet Bharara, the US attorney in New York.

"With today's indictment, Dunki joins the ranks of many other individuals this office has charged in connection with hiding money in offshore bank accounts from the Internal Revenue Service."

Dunki is charged with one count of conspiracy to defraud the US Internal Revenue Service, a charge which brings a maximum five years in prison.

Dunki, 66, lives in Switzerland and has not been arrested, the justice department said.