Jack Lemley has resigned as chairman of the Olympic Delivery Authority (ODA), the group responsible for the construction of London 2012 venues.
Lemley, who took up the post in November last year under a four-year contract, said he wished to return to work at his international construction consulting firm in the US.
“It has been a privilege to chair the ODA for the last year and lead the organisation through its formative stages,” he said in a statement.
“The board is now established along with its separate planning function.
The delivery partner has been appointed and the ODA is ready to move to the next stage of its development.
I am keen to return to the helm of my international construction consulting firm in America, which is increasingly busy with major contracts.”
He added: “I have every confidence that London will stage a superb Olympic Games and Paralympic Games in 2012 and leave a legacy that the country can be proud of.”
Sir Roy McNulty, who has been chairman of the Civil Aviation Authority since 2001, has become acting chairman of the ODA.
A consortium led by UK contractor, Sir Robert McAlpine, recently entered negotiations over the design and construction of the main stadium for the Olympic Games.
Team McAlpine includes Kansas City-based sports and design architect, HOK Sport, structural engineer, Buro Happold of the UK, and US services engineer, M-E Engineering.