The panel also credited the company's ex-CEO, Michael Woodford, for bringing the deception at the camera and medical equipment maker to light. Woodford, a Briton, was fired in October after questioning the dubious transactions that have become one of Japan's biggest corporate fiascos.
Led by former Supreme Court judge Tatsuo Kainaka, the third-party panel found that as of 2003, Olympus had racked up 117.7 billion yen ($1.5 billion) in investment losses dating back to the 1990s.
"The management was rotten to the core and contaminated what was around it, creating in the worst sense a group mentality of the typical salarymen," the report said in a reference to Japan's culture of corporate loyalty.
It said it found no involvement of "anti-social groups," a euphemism for Japanese criminal gangs, as some news reports have speculated. The panel said it traced the money and the various funds used to cover up investment losses, and no underworld groups were involved.