John Tiner, the CEO of the Financial Services Authority (FSA), announced his resignation yesterday.
He will leave in July 2007, having held the post for four years.
Tiner said that he was leaving because he wanted to take up a fresh challenge in the private sector, before thinking about retirement.
He joined the FSA in April 2001 as managing director of the consumer, investment and insurance directorate and was appointed chief executive in 2003.
FSA chairman Callum McCarthy said:
"He has been a leader in developing international regulation through his work in Europe. Within the FSA, he has been invaluable in developing and leading a management structure with discipline and enthusiasm."
Rather bizarrely Tiner will remain an employee of the FSA until January 2008, during which time he will be excluded from any work within the financial services sector or for any UK listed company.