Chuck Prince yesterday quit as chairman and chief executive of Citigroup as the company revealed it was facing between $8bn and $11bn of further losses on its holdings of mortgagerelated securities.

Mr Prince said that in the light of the losses stepping down was "the only honourable course" for him to take. The writedowns will put further pressure on Citi's weakened balance sheet, which last week prompted analysts to raise questions about the sustainability of Citi's dividend.