A former UBS banker and an adviser from Liechtenstein have been charged with helping clients, including California real-estate billionaire Igor Olenicoff, avoid paying taxes, according to a published report.

Bradley Birkenfeld, who worked at UBS from 2001 to 2006, appeared in court Tuesday. He is alleged to have helped clients use secret bank accounts and file false tax returns, according to a report in The Wall Street Journal. See story in WSJ.com

The case could lead to other U.S. clients as Birkenfeld and Mario Staggl, who owns a trust company called New Haven Trust in Liechenstein, courted rich Americans, the newspaper reported.

The indictment against the pair doesn't mention UBS by name, referring only to a Swiss bank, according to the Journal.