Olympus has defended paying $687m to financial advisers but refused to comment on its former CEO’s claims that the cash was channelled to ‘unknown parties in the Cayman Islands’.

Asked why Olympus paid such a high fee in relation to its buy-out of medical equipment firm Gyrus in 2008, Olympus’s Tokyo spokesman Ayako Nagami said this morning: ‘The amount paid to the adviser has been approved by a third-party firm.’

Yesterday, ousted CEO Michael Woodford repeated his claims of financial wrongdoing after Olympus admitted it had paid advisers $687m – an amount Woodford questioned with Olympus management before he was fired.

Japanese camera giant Olympus will set up an independent panel to review previous takeovers after its sacked chief executive has raised questions about the “improper payments”.

In a stock exchange announcement in Tokyo, Olympus confirmed that it would set up an “independent committee consisting of experts including lawyers and accountants” to investigate previous merger and acquisition deals.

Following his allegations, the share price of Olympus plunged by almost 50 per cent and some of its biggest shareholders, including Nippon Life and Harris Associates, demanded answers.

A former Wall Street banker of Japanese descent has emerged as a key figure in the scandal, according to documents provided by the firm’s ex-CEO.

The veteran banker, Hajime ‘Jim’ Sagawa, owned an obscure U.S. financial firm which was hired by the endoscope-maker five years ago to provide what later turned out to be stunningly expensive advice, a fee of $687 million, the documents show.

Former Olympus CEO Michael Woodford, barely a fortnight into his tenure in the top job, raised the alarm on the huge advisory fee after his sudden sacking last week. The sum was equal to a third of the 2008 takeover deal to which it related — compared with the 1-2 percent bankers usually charge.

Woodford, now in the UK, had a copy of an independent inquiry into the fee, which was paid in relation to Olympus’s $2.2 billion takeover of UK medical equipment firm Gyrus. He had commissioned the inquiry from accountancy firm PricewaterhouseCoopers (PwC) while he was still an executive.

PwC has declined to comment on the report, which is marked confidential and carries no date for when it was compiled.

Olympus, which denies any wrong-doing over the fee payment, has not given details on the identities of the advisers who earned the fee, other than acknowledging that the fees were paid to two obscure firms, AXES and AXAM Investments.