Mizuho Financial has responded to the sharp fall in Japanese share prices with plans to sell Y900bn ($9.1bn) of shares in its own domestic banking clients, or about 30 per cent of its vast portfolio.

The plan, approved by Takashi Tsukamoto, incoming chief executive, is designed to insulate Mizuho against the sort of sharp stock market declines that have cost it hundreds of billions of yen during the current financial crisis.