It comes after Clegg led Britain to its most successful Olympic performance for a century at Beijing.

 

The team finished fourth overall behind superpowers China, the United States and Russia with 47 medals, including 19 gold.

 

But Clegg had already been told before the team left for the Chinese capital that he would be replaced as chief executive of the BOA by chairman Colin Moynihan.

 

Clegg was acknowledged to be a brilliant organiser but Moynihan believed that he was not fully realising the commercial potential of the BOA in the build-up to the 2012 Games, which has brought the chairman into conflict with leading organisers at London, who own the chief marketing rights to the Olympics, including the famous five-rings.

 

Clegg was replaced by Andrew Hunt, formerly head of a security company, who will work alongside a new chief commercial officer, Hugh Chambers, and a new communications director, Adam Parsons, a BBC television journalist, as Moynihan has strengthened his power-base at the BOA.

 

Clegg managed British athletes at the last 12 Olympic and Olympic Winter Games, the most recent six as the Chef de Mission. 

 

Clegg had joined the BOA in January 1989 as its assistant general secretary after a successful career in the Army which included a period as manager of the British Biathlon Team.

 

He was subsequently appointed deputy general secretary before becoming the BOA's first chief executive in January 1997.

 

But his greatest contribution to British sport will be being the driving force behind London's bid to stage the Olympics, an idea he first started working on shortly after being appointed as chief executive.

 

It was him who persuaded the then Mayor of London, Ken Livingstone and the Government of the merits of a London bid to stage a future Olympic Games.

 

On returning from Singapore, where he was one of three British signatories on the 2012 Host City contract, he led a meeting of Olympic national governing bodies and national agencies to set a target of aspiring to finish fourth in the 2012 medal table - a target they achieved ahead of schedule in Beijing.

 

Clegg said: "The organisation is moving in a different strategic direction and it was always going to be difficult for me, but I am glad to be leaving on a high after Beijing.

 

"Before Beijing I advised the Olympic governing bodies that I felt our results could be good enough to achieve our 2012 goal four years early.  

 

"Before the start of the Games I predicted that Team GB would win 17 gold, 10 silver and 20 bronze medals.

 

"Whilst the final results exceeded even my own expectations such an achievement was always going to present me with a personal dilemma, just as it has proved.

 

"I have therefore taken the decision that now is the right time for both myself and the BOA to move on to new challenges and to allow others to build on the success which has been achieved.

 

"It has been a huge privilege to manage our country's finest athletes in this environment on so many occasions; I hope that in some small way I have helped to contribute to any success they have achieved.

 

"This has not been an easy decision but I know that it is the right one."

 

But Clegg will continue to work on London 2012 as an adviser.

 

Sebastian Coe, the chairman of London 2012, said: "Simon's experience, particularly in terms of preparing Olympic teams, is second to none anywhere in the world - as was so recently demonstrated in Beijing.

 

"He has championed our vision to put athletes at the heart of our Games and we hope he will continue to help shape the London 2012 Games through our sports advisory group."

 

Moynihan said: "Simon's leadership over the last 12 years as our chief exeutive has positioned the BOA as one of the most respected and leading National Olympic Committee's in the world.  

 

"His skills and experience particularly in the Olympic environment as Team GB's Chef de Mission will be greatly missed and everyone in the Olympic Movement in the UK wishes him well for the future."

 

Sir Steven Redgrave, the five-time Olympic gold medallist and a vice-president of the BOA, said: "Simon's vision, understanding and attention to detail have consistently provided Team GB athletes with a real competitive advantage at the Olympic Games.

 

"I've known him for over 20 years and I know that I speak for many athletes, both medallists and non medallists, when I say that his support, encouragement and athlete focussed management style will be difficult to replace. 

 

"He has played an important part in our lives and we are sure that he will go on to achieve future success in whatever path he chooses."