Ken Lewis, the embattled chief executive of Bank of America, is to step down in December, leaving the country’s biggest lender without a successor and capping a period of turmoil in the executive offices of leading US financial groups.

Mr Lewis’ surprise departure, announced on Wednesday night, ends a turbulent eight-year tenure at BofA and comes days after Morgan Stanley, JPMorgan Chase and Wells Fargo made sweeping changes to their top ranks.