Chiyoda Mutual Life Insurance Co., which is in the process of restructuring under the corporate rehabilitation law, is planning to sue former board members for billions of yen in damages over policies blamed for causing its effective bankruptcy, company sources said Sunday.

The Tokyo-based life insurer said it will ask the Tokyo District Court as soon as Wednesday to begin damages evaluation procedures, the sources said.

The company's former management has one month to file a complaint against such action after the request for damages evaluation is accepted by the court.