A former UBS AG banker has been charged with conspiracy for helping wealthy Americans hide assets to evade U.S. income taxes, according to a criminal complaint unsealed on Tuesday in federal court in Florida.

Christos Bagios, who now works for Credit Suisse , was accused of assisting U.S. clients in a bid to conceal their assets and income from the U.S. government when he worked at UBS from 1999 through 2005, according to the complaint.

It said Bagios, a Greek citizen, had as many as 150 undeclared U.S. clients with total assets under management of $400 million to $500 million while at UBS.

Bagios, 45, was arrested in New York on January 26 and later transferred to Fort Lauderdale, Florida, where he made an initial court appearance on Tuesday in handcuffs and clad in a beige prisoner outfit.

He and others at UBS marketed undeclared Swiss bank accounts and Swiss bank secrecy to wealthy United States clients who were interested in attempting to evade United States income taxes, the complaint said.

Bagios is currently the head of Credit Suisse's Relationship Management West Coast group, a private banking unit that is part of Credit Suisse Private Advisors, according to the bank's website.

The charges against him appeared to have no direct connection with the case of four other individuals at a Swiss bank, identified by sources with knowledge of the situation as Credit Suisse, who were charged last week with helping Americans dodge U.S. taxes in a widening probe into offshore banks.

Credit Suisse spokesman David Walker had said the bank is cooperating with authorities in the case of the four current and former bankers named in last week's indictment filed in the U.S. District Court for the Eastern District of Virginia. Walker also said the bank was not a target in that case.

U.S. officials are investigating other banks after UBS in the past two years paid $780 million and agreed to hand over nearly 5,000 account names to the U.S. government to settle tax evasion charges.

During the court proceedings, U.S. Department of Justice officials said they had reached out to Bagios to see if he would cooperate with ongoing tax fraud investigations but said he had not responded.

Much of the complaint centered on testimony from another former UBS banker, Renzo Gadola, a Swiss citizen who in December pleaded guilty in a Miami federal court to assisting Americans hide their money from U.S. tax authorities.

Kevin Downing, a top Justice Department prosecutor who spoke by telephone during Tuesday's hearing, said Bagios and Gadola worked together in a UBS unit focused on helping American tax evaders.

Bagios did not comment on the charges but his lawyers sought to have him released and the case against him dismissed, on grounds that officials had failed to charge him within time limits laid out under U.S. statues.

A federal judge ruled that Bagios remain under arrest and a new hearing in the case was set for Wednesday morning.

(Additional reporting by Jeremy Pelofsky in Washington and Tom Brown in Miami; Editing by Gary Hill)