HECTOR Sants has resigned as the head of the Financial Services Authority (FSA) in a move that throws the future of financial regulation into doubt.
Sants had been a major figure in the massive shake-up of banking reform following the global financial crisis.
He has also spoken out against plans by the Conservatives to scrap the FSA if they get into government.
Sants, who will leave the post in the summer, said: "When I was appointed I told the board that I planned to serve as CEO for three years, and I intend to stick to that timetable.
"Of course, those three years have encompassed the most extraordinary circumstances for a financial regulator, and I am very proud of the manner in which the FSA rose to the challenge of dealing with such unprecedented turbulence across global financial markets.
"Moreover, I believe the FSA candidly examined the failings in financial regulation that contributed to the onset of the crisis, learned the lessons and has gone on to reform itself into a much stronger and better equipped organisation.
"The success of any regulatory structure depends on ensuring supervision is carried out by high-quality supervisors with sufficient resources and specialist support.
"I believe the FSA has made great strides in ensuring that such individuals are in place in the UK and I am sure that after I leave they will continue to do invaluable work to ensure financial stability and protect the interests of consumers."
Sants has worked at the regulator since 2004 after he joined from Credit Suisse First Boston.
John McFall, chairman of the Treasury Select Committee said: "I think it is rather unfortunate. Hector Sants was leading the FSA at a time when it was making real progress. Discontinuity at this time is perhaps not helpful to financial stability but he has made his decision."