Two top-10 shareholders said Bolland still had time to make improvements following a boardroom overhaul last year.

The chief executive of one of the country's biggest food groups has resigned following a boardroom bust-up.

Ushioda's move follows a boardroom drama that has been unusually fractious, at least by the standards of corporate Japan.

The deal may have been complicated by HSBC's recent change in its chairman and chief executive following a boardroom power struggle.

Mr Charles Wigoder, who left the business in January following a boardroom row, still holds about 10 per cent of the company.