Nissan Motor Co. Chief Executive Officer Hiroto Saikawa signed off on Carlos Ghosn's retirement package, an outside corporate-governance panel said, which could intensify scrutiny of his role in alleged financial improprieties by the former chairman of Nissan and Renault SA.

Tokyo prosecutors have accused Nissan, Ghosn and his deputy, Greg Kelly, of misleading investors and the government about how much the company was paying its top executive. Although they have been charged with under-reporting Ghosn's compensation, it wasn't clear how much of that was deferred for retirement.

As part of a set of recommendations for a more independent board at Nissan released Wednesday, a special governance committee included a cryptic line about Ghosn's retirement package: "Regarding the post retirement treatment of Mr. Ghosn, Mr. Ghosn, through Mr. Kelly as the person responsible for Global Human Resources and Legal, obtained documents signed by the current CEO."