Embattled auto industry executive Carlos Ghosn had amassed so much power that he was able to hamstring Nissan Motor Co.'s legal and compliance departments, preventing effective in-house oversight and allowing him to hide alleged financial misdeeds for years, according to a new report from the Japanese carmaker.

Nissan's seven-member special committee for improving governance found that a “personality cult” had developed at the company, where “Mr. Ghosn was in a way deified within Nissan as a savior who had redeemed Nissan from collapse, and his activities were deemed impenetrable territory within the company.”

A whistleblower spurred Ghosn's ouster as Nissan's chairman. He now faces criminal charges alleging he misused company funds and underreported more than $44 million in income during a five-year span. Ghosn's apparent right-hand man, former Nissan director Greg Kelly, also faces charges in connection with the alleged scheme.