In a statement, Mitsubishi Materials said its president Akira Takeuchi will step down from that role and assume the position of chairman after an annual shareholders meeting on June 22. Current executive vice-president Naoki Ono will take over from Takeuchi as president, a role that carries responsibility for executing strategy at Mitsubishi Materials.

The boardroom shake-up comes a few days after the firm said it had found fresh cases of misconduct at its Naoshima copper smelter and refinery in western Japan. The plant's Japanese Industrial Standards (JIS) certification has been revoked.

That finding followed a company announcement a month earlier that it had found new cases of improper action at a small number of its group firms, widening the number of affected customers from 762 to an undisclosed figure.

The scandal is one of a series of quality assurance frauds to rock Japanese manufacturers. Since October, Japan has seen revelations of data tampering and compliance failures at Kobe Steel Ltd, Toray Industries Inc, Nissan Motor Co Ltd and Subaru Corp.

Shares in Mitsubishi Materials were up 0.2 percent as of 0545 GMT, underperforming the broader Topix <.TOPX> which was up 0.4 percent.

(Reporting by Yuka Obayashi; Editing by Kenneth Maxwell)