The London Olympics in 2012 are set to fall short of a target to source at least 20% of energy from new local renewable schemes.
David Stubbs, head of sustainability at the London Organising Committee of the Olympic Games (LOCOG), told the London Assembly's environment committee it is increasingly unlikely the target will be met.
This is partly due to the cancellation of a wind turbine scheme and a lack of other large-scale renewable energy projects in the city.
Committee chairman, Darren Johnson, said: 'London said it would provide the greenest Games ever and although good progress is being made in many areas, it is disappointing that organisers don't expect to meet their renewable energy target.
Another potential setback for Olympics organisers is lack of progress on developing new waste processing facilities.
Food and food packaging is expected to make up 40% of waste during the games and it was hoped this would mean the creation of a new organic waste processing facility in East London.
But Shaun McCarthy, chairman of the Commission for Sustainable London 2012, said this was not likely to happen in time for the summer of 2012 although he hopes one will be created after the games.
In better news, significant amounts of clean energy generation will take place in and around the Olympic Park.
Biomass boilers, which burn waste wood, and some 50,000 square metres of solar panels will be installed.
Plans are also in place for a small scale Combined Heat and Power biomass plant which would be handed onto the legacy company after the games.