By Sumio Ito and Reiji Murai
Briton Michael Woodford, whose sacking and revelations about irregular deals and payments exposed the scandal, said he would meet the company-appointed panel of investigators in London, New York or Singapore.
"I think there are security issues in relation to Japan," Woodford told Reuters in a phone interview from Britain. "They only have to get on a plane."
Woodford did not explain his concerns but the scandal has raised fears -- denied by Olympus -- that the deals could be linked to "anti-social forces", a euphemism in Japan for organized crime.
Olympus has been under intense pressure to explain deals that have rattled confidence in the 92-year-old company and wiped out half its market value.
The company has repeatedly denied any wrongdoing. Woodford raised alarm bells over the deals publicly after he was sacked on October 14 just two weeks into the job of CEO.
This week the endoscope and camera maker set up a panel of six men to investigate the deals, which include the world's most generous advisory fee of $687 million, mostly paid to an obscure Cayman Islands firm.
In a sign of concern the scandal may hurt investor confidence in Japan, the ruling Democratic Party plans to set up its own panel to debate improving corporate governance and disclosure, a senior party official said on Wednesday.
At the center of the scandal is the 2008 acquisition of British medical equipment maker Gyrus for $2.2 billion that involved an advisory fee of $687 million, about a third of the buying price and way above the industry standard of around 1 percent.
The Olympus panel will also focus on the acquisition of three firms in Japan that Olympus, under chairman Tsuyoshi Kikukawa's decade-long reign at the company, later largely wrote off.
Woodford has brought the deals to the attention of regulators in Britain, Japan and the United States. Olympus' chairman has resigned over the revelations.
A review in 2009 commissioned by Olympus' auditing board cleared management of misconduct in the now-controversial acquisition of the three Japanese firms.
Adding to the heat on the company, a Japanese investor threatened to file a shareholder suit against the managers responsible for the deals, in what would be the first legal action over the acquisitions.
Seeking to assure skeptical investors, Olympus has said no one on the all-Japanese panel had any previous association with the company.
Still, some analysts said the company will need to go further to provide reassurance about the integrity of the panel's role, while Woodford said he had reservations.
"The material will be fed and filtered by Olympus, they need forensic accountants to report to the committee because you don't want Olympus to provide the data, you want accountants to provide the data," the Briton said.
"What exactly is the brief of the committee -- this should be painted crystal clear on the website of Olympus. I don't see that here," he said. "If the committee does what needs to be done it is not going to look good for half or more of the board -- there is no way it can."
The group, besides Kainaka, includes lawyers and an accountant with experience investigating governance at a bank, power company and consumer electronics maker.
It includes Hideki Nakagome, a retired judge who served on a panel investigating Tokyo Electric Power's nuclear accident at its Fukushima plant.
Also named was ex-prosecutor Tomoyoshi Arita and two lawyers from private practice, Eiji Katayama and Osamu Sudo. The latter chaired a group investigating JVC Kenwood Corp, which last year was forced to issue a warning about its status as a going concern. Katsuaki Takiguchi, an accountant, rounds off the panel.
Katayama, Sudo, Kainaka and Nakagome have not handled cases involving mergers and acquisitions, legal filings from legal publisher Westlaw Japan's database show.
(Writing by Tim Kelly, Tomasz Janowski and Mark Bendeich; Editing by Neil Fullick and Dean Yates)