In a detailed report titled "Going for Green" the Assembly praises efforts to reduce carbon emissions, recycle waste, avoid sending rubbish to landfill and use a fleet of low-emission Olympic vehicles.

But it warns more must be done as the big occasion gets closer and fears that environmentally the Olympic and Paralympics may not be as "transformative" as originally hoped.

Failing to secure more electric vehicles for the Olympic fleet was a "missed opportunity" and a target on renewable electricity during the staging phase of the Games is unlikely to be met.

There are forecast to be harmful levels of the pollutant nitrogen dioxide (NO2) in crucial parts of London in 2012 as the capital's air quality has not improved as hoped since 2005.

"Going for Green" is calling for action to ensure NO2 levels are reduced to bring them closer to EU limits by the time of the Games.

Darren Johnson, chairman of the London Assembly Environment Committee, said: "We fully support London 2012's ambition to be the most sustainable Olympic and Paralympic Games in recent history, and there has been some excellent work towards that goal.

"However, we don't want to see environmental standards compromised in the run-up to what I am sure will be a fantastic Games.

"London's air quality is a particular cause for concern, as failing to reduce levels of pollutants could have consequences for London's international reputation as well as the health of those attending the event.

"We also need to see clear targets for re-using temporary materials, more detail on how organisers will promote sustainable travel and plans for recycling facilities on site and around London."

The report says London's 2012's approach to mapping its carbon footprint is "groundbreaking" and it welcomes the organisers' aim to re-use or re-cycle 90 per cent of temporary materials.

However, it also sets out work that is still needed to help ensure the Games lives up to its environmental aspirations.

The Going for Green report will be considered for formal agreement on December 1.