FORT LAUDERDALE, Fla. (TheStreet) -- A former UBS (UBS) - Get Report banker convicted of helping wealthy clients dodge taxes will spend as much as 40 months in federal prison.

The sentencing comes just days after the Swiss banking giant reached a settlement with the U.S. government, under which UBS agreed to submit the accounts of 4,450 clients accused of tax evasion to the scrutiny of tax authorities.

The 44-year-old banker, a U.S. citizen named Bradley Birkenfeld, was initally only a whistle-blower when, two years ago, he handed over to investigators key evidence that helped the U.S. pursue its wide-ranging tax-fraud case against UBS and others.

But it turned out that Birkenfeld, who lived and worked in Switzerland for 15 years, had declined to mention to prosecutors that he himself had assisted clients through illegal tax loopholes.

After Birkenfeld pleaded guilty to one fraud conspiracy charge, U.S. District Judge William Zloch gave the banker a stiffer sentence even than that sought by his prosecutors, who'd recommended 2.5 years of jail time.

Attorneys for Birkenfeld, who also was fined $30,000, argued for only probation.

Still, U.S. authorities praised the banker and his role in the wider investigation into the use of secret Swiss accounts to hide assets from the IRS.

"Without Mr. Birkenfeld walking into the door of the Department of Justice in summer of 2007, I doubt this massive fraud scheme would have been discovered by the United States government," Kevin Downing, the senior trial attorney in the Justice Department's tax division, told

The Associated Press

.

Birkenfeld said he refrained from telling investigators about his own role in the tax crimes because he feared Switzerland's strict banking-disclosure laws. U.S. authorities say he would have been protected from Swiss prosecution.

Three other Swiss bankers and a Swiss lawyer also are facing U.S. criminal charges. Four U.S. clients of UBS have already pleaded guilty and at least 150 more are under investigation.

-- Written by Scott Eden in New York

.

Copyright 2009 TheStreet.com Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed. AP contributed to this report.