The move comes in the face of mounting criticism that the London Olympics will be remembered for being a 'flat pack' games, with design being sacrificed.
Both Richard Rogers and London mayor Ken Livingstone have openly expressed their concerns over the dependence on design-and-build contracts as a procurement method.
It is understood that the letter stresses the importance of the Velo Park competition, for which the ODA has said it has received more than 100 expressions of interest.
An ODA spokesman said: 'There has been a lot of static around the games that this will be the 'flat pack games', but this is not how we want people to see the 2012 Olympics.
'We want to stress the importance of top design throughout the Olympics, as well as in the Velo Park competition.'
The letter also contains further information about the judging panel, which will include ODA design adviser Ricky Burdett, RIBA president elect Sunand Prasad and president of the Landscape Institute Nigel Thorne.