Olympus Corp <7733.T> on Tuesday revealed members of a panel, including a former Japanese supreme court judge, that it pledges will conduct an independent probe into past M&A deals at the core of a scandal engulfing the endoscope maker.

It picked the group of six, including five lawyers and an accountant, based on guidelines on third-party panels issued by the Japan Federation of Bar Associations, Olympus said in a statement.

None of the six have had any previous association with the company, an Olympus spokeswoman said. As yet, no deadline for the group to report its findings has been set, she added.

The panel will look into $687 million (428 million pounds) in payments made to a financial adviser for the $2 billion purchase of British medical equipment maker Gyrus in 2008 and the acquisition of three companies in Japan that Olympus, under former chairman Tsuyoshi Kikukawa, later largely wrote off.

Investors are closely watching for any attempt by the management to appoint investigators who may be sympathetic to the their position.

The head of the Tokyo Stock Exchange on Friday warned that the company risked legal action from shareholders unless the probe was thorough and unbiased.

Major shareholders are also clamouring for disclosure of what went on in the Olympus boardroom when it agreed to the adviser fees and acquisitions at home.

Southeastern Asset Management, the largest non-Japanese investor, wants the company to publish minutes of board meetings related to the series of payments.

Pressure on the firm to clean house has also come from Japan's prime minister, Yoshihiko Noda, who asked the company for clarification in an interview in the Financial Times.

Chairing the panel is Tatsuo Kainaka, who served as a supreme court judge in Japan from October 2002 to January 2010.

(Reporting by Tim Kelly; Editing by Edmund Klamann and Chris Gallagher)