Josef Ackermann, chief executive of Deutsche Bank, has called for a thorough overhaul of the operations of investment banks and regulators to combat a loss of investor confidence in complex finance.

Banks needed to make complex structured products, such as mortgage securities, far more transparent and thus reduce investors' dependency on credit ratings, Mr Ackermann said. "Improved transparency is decisive, including disclosure of off-balance-sheet exposures, such as structured investment vehicles," he said in a private speech to the London School of Economics this week, which the bank is circulating to key clients and regulators.