Citigroup is preparing for the departure of Anil Prasad, the most senior banker in its troubled foreign-exchange business.

Prasad, who joined the bank in 1986, was appointed as the global head of foreign exchange and local markets in 2007. Under his tenure, the bank's currencies business regained lost ground from competitors to become the second-biggest bank in the industry, according to Euromoney's benchmark market-share survey.