By Carlyn Kolker

NEW YORK, Feb 6 (Reuters) - U.S. prosecutors on Thursday announced they indicted Peter Amrein, a Swiss asset manager, on charges that he assisted U.S. taxpayers in evading millions in taxes by hiding money in offshore trusts at multiple Swiss banks.

Prosecutors accuse Amrein, who worked at an unidentified asset management firm, of working with Edgar Paltzer, a Zurich-based lawyer who pleaded guilty in Manhattan federal court in August to assisting U.S. clients commit tax fraud by opening bank accounts in Switzerland that shielded them from U.S. authorities. Paltzer agreed to cooperate with prosecutors.

Amrein, 52, is a Swiss citizen and has not been arrested, prosecutors said. An attorney for Amrein could not be identified.

U.S. prosecutors have deepened their probe of Swiss banks that they say have abetted tax evasion for decades. The U.S. Department of Justice has targeted 14 Swiss banks for allegedly offering hidden offshore accounts to help clients avoid taxes.

In February 2009, UBS AG became the first bank to settle with the U.S. government, agreeing to pay $780 million and entering into a deferred prosecution agreement with prosecutors.

Wegelin, the oldest Swiss bank, announced it would close after pleading guilty in January 2013 to helping wealthy U.S. citizens avoid paying taxes, resulting in orders that it pay around $74 million.

SHAM FOUNDATIONS

Amrein helped U.S. clients open and keep offshore accounts in at least five Swiss banks, including Wegelin, from the late 1990s until 2012, U.S. prosecutors allege in the indictment, which was filed in federal court in New York.

These included accounts under the names of sham foundations based in Liechtenstein. Amrein worked with Paltzer to set up these foundations.

The accounts were not declared to U.S. authorities, and U.S. taxpayers did not report them on U.S. tax forms.

Amrein, who worked first as a client advisor at a bank and later became an asset manager at a Zurich-based asset management firm in 2006, continued to help U.S. citizens hide their money offshore, even as U.S. authorities' crackdown on offshore accounts became widely known, prosecutors said.

Amrein helped clients find new banks where they could conceal their money as the crackdown spread, prosecutors said.

He also helped a U.S. client withdraw money from an undeclared account in small increments so it would not be detected by authorities, prosecutors said.

Amrein is charged with one count of conspiracy and faces up to five years in prison.