Tucked away inside Citigroup is one of the world's largest investment banks. But after a lacklustre fourth quarter, reported yesterday, it is time to ask whether this giant unit might weigh on the bank's recovery prospects.

Securities and banking, part of Citigroup's core businesses, had about $800bn (€559bn) of assets at year-end, giving it a balance sheet similar in size to those of Morgan Stanley's and JP Morgan Chase's investment banks.