Financial Services Authority chief operating officer Richard Farrant is to quit the watchdog this month.
Farrant is one of three managing directors sitting on the board below chairman Howard Davies. He is just 15 months into a three-year contract worth £210,000 a year.
Farrant is the most senior departure to hit the watchdog. He is in line for an estimated pay-off of about £370,000.
His responsibilities for finance, business planning, information services and premises will be taken by Paul Boyle.