A report issued by the London Assembly's Environment Committee warns that there is still significant work to be done if the 2012 Olympic and Paralympic Games are to achieve their environmental aims.

The report, 'Going for Green', praises efforts to make London 2012 the most sustainable Games in recent history, and notes the innovative work undertaken to map and reduce the event's carbon emissions and avoid sending waste to landfill through recycling.

However, the report also states that the Games may not achieve the environmental targets originally hoped for, and observes that it is still unclear how carbon emissions will be reduced.

London's air quality has not improved as anticipated since 2005, and there are growing concerns that by 2012 parts of London will be subject to harmful levels of pollutant nitrogen dioxide (NO2). The report comments that the failure to secure more electric vehicles for the Olympic fleet is a ''missed opportunity''.

The report calls for greater clarification on a number of the Games' environmental policies, and recommends that: organisers more effectively quantify carbon savings; that the Mayor of London should publish concentrated NO2 modelling (taking into account Games related activity); that plans should be set out for best-practice recycling facilities; and that targets should be set for the re-use of temporary materials.

The event's organisers were criticised in July after the Assembly found the Games will fail to meet its target of obtaining 20 per cent of its electricity through local renewable sources. This was largely due to the abandonment of plans to build a wind turbine in the Olympic Park, following changes to health and safety legislation.

Environment Committee chairman Darren Johnson 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.''

''We 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.''