Credit Suisse Group Inc lost its bid to sever National Century Financial Enterprises Inc co-founder Lance Poulsen as a defendant in an upcoming scheduled trial over fraud at the health care services company a decade ago.

Thursday's decision by U.S. District Judge James Graham increases the potential that evidence harmful to the Swiss bank's defense may be introduced at the trial, where Credit Suisse faces a potential $2 billion of exposure.

The state of Arizona, AllianceBernstein Holding LP , Lloyds TSB Bank Plc <48IY.L>, MetLife Inc , Allianz SE's Pimco unit and other bondholders accused Credit Suisse, once a placement agent for National Century bonds, of deceiving them about that company and missing its estimated $2.9 billion fraud.

Poulsen co-founded National Century in 1990, and is the only other defendant remaining in the case. He is serving a 30-year prison term and is presumed insolvent.

(Reporting by Jonathan Stempel in Washington, D.C.; Editing by Gerald E. McCormick)