New York City ? Citigroup Inc. Chairman and Chief Executive Charles Prince, beset by the company’s billions of dollars in losses from investing in bad debt, resigned Sunday and is being replaced as chairman by former Treasury Secretary Robert Rubin.

The nation’s largest banking company announced Prince’s widely expected departure in a statement following an emergency meeting of its board. Citi also said Sir Win Bischoff, chairman of Citi Europe and a Member of the Citi management and operating committees, would serve as interim CEO. Rubin, a former co-chairman of Goldman, Sachs & Co., has served as the chair of Citi’s executive committee, and it was also expected he would take a greater role in leading the company.

In a separate statement, Citi, which took a hit of $6.5 billion from asset writedowns and other credit-related losses in the third quarter, said it would take an additional $8 billion to $11 billion in writedowns.

Prince joined former Merrill Lynch & Co. CEO Stan O’Neal, who resigned from the investment bank last month, as the highest-profile casualties of the debt crisis that has cost billions at other financial institutions as well.