Turmoil at Japan's Nissan Motor surrounding allegations of impropriety by ousted chairman Carlos Ghosn raises questions about the oversight role of the company's board of directors, corporate governance experts said this week.
Ghosn, long seen as a superstar of the global auto industry, was arrested last month after allegedly under reporting compensation and misusing assets.
He gained renown for reviving Nissan after French automaker Renault took a large stake in the company nearly two decades ago. He later went on to oversee an alliance involving Renault, Nissan and Mitsubishi Motors.
But Ghosn was dumped by the boards of Nissan and Mitsubishi after his arrest on Nov. 19, though is still chairman and CEO of Renault. He remains in custody in Tokyo and has yet to be charged.
Japanese broadcaster NHK, citing unnamed sources, reported last month that Ghosn has denied under reporting his earnings.
Jamie Allen, secretary general of the Asian Corporate Governance Association, said that a key concern about the allegations against Ghosn is why Nissan's board of directors was seemingly unaware.
"I think there is a clear issue of internal controls in that company that they're not properly addressing," Allen told reporters in Hong Kong on Wednesday.
"If the board really didn't know about that, and maybe they really didn't know about that, then that doesn't speak ... very highly of their internal controls, or their governance," Allen said. "My point is boards have collective responsibility ... so I think the board at Nissan really needs to do some soul-searching."
Other experts also questioned the role of oversight at Nissan.
"I think it is extremely unlikely that the board did not know about this," Jesper Koll, head of Japan at WisdomTree Investments, told CNBC on Friday.
"Because the reality is any board, whether it is a purely local Japanese company or whether it is an international, global company, whatever corporation you run, the executive compensation and CEO compensation is an extremely important issue," Koll said.
John Buchanan, an expert in Japanese corporate governance at the Centre for Business Research at Cambridge Judge Business School, said that a lack of formal charges against Ghosn makes it difficult to assess the board's role, though he added it was unlikely to have been completely in the dark regarding remuneration.
And Nissan's decision to "disgrace the company by calling in public prosecutors" resulted in "effectively advertising the inadequacy of the board and Nissan's internal controls," Buchanan said in an email.
"This can be seen as a demonstration that Japanese corporate governance is still largely internally focused," he said.
Contacted by CNBC for comment, Nick Maxfield, a spokesman for Nissan, which is headquartered in Yokohama, Japan, said by email that the company went to Japanese prosecutors with results of an internal probe spurred by a whistleblower that had "uncovered substantial evidence" of alleged under reporting of compensation and misuse of assets and funds.
Maxfield, who said Nissan could not disclose specifics of the probe, referred to comments made by Nissan CEO Hiroto Saikawa at a press conference the day Ghosn was arrested.
Saikawa had said Nissan would need to "identify the issues of governance (and) really look back on what happened seriously and take immediate and fundamental countermeasures" because the alleged misconduct had been lengthy.
Maxfield also said that Nissan's board on Nov. 22 vowed to create a special committee to receive advice from an independent third party on governance and managing compensation.
A team of Jefferies analysts suggested in a report last month that foreign shareholders — who, by their calculation, hold more than 80 percent of Nissan's stock — also cannot shirk responsibility.
"If Nissan was badly governed, then the blame should rest squarely on the shoulders of its foreign majority shareholders," the report said.
Renault has the largest single stake in Nissan at more than 40 percent.
The European automaker did not immediately respond to a request by email for comment from CNBC.
Some experts also cautioned against reading too much into Nissan's problems and losing sight of positive changes that have taken place in broader Japanese corporate governance in recent years, such as greater power for whistle-blowers — a key element of the Nissan case — and a new ombudsman clause.
"That actually shows, I think, that corporate governance in terms of the structure that is being put into place is actually looking to improve," WisdomTree's Koll said.
Ulrike Schaede, professor of Japanese Business at the University of California San Diego, agreed that the overall situation has improved, but stressed that corporate abuses will occur even with the best of safeguards.
"If a CEO wants to do something that benefits him or her more than the company, they will be able to do it no matter what the governance system does," Schaede said.
"It happens in all systems," she added. "So in that sense I don't think that this is indicative of a system failure in Japan."