Councils opposed to expansion at Heathrow are launching a legal challenge to the Government's decision to approve a third runway at the west London airport.
At the High Court in London, the 2M group - representing 23 authorities - is applying for a judicial review of the expansion given the go-ahead in January this year by Transport Secretary Geoff Hoon.
The case is being backed by London Mayor Boris Johnson, who favours an alternative Thames estuary airport site.
Green groups such as Greenpeace, the Campaign to Protect Rural England and the Royal Society for the Protection of Birds are also supporting the legal action.
The local authorities will argue that the Government failed to conduct a lawful consultation process and arrived at a decision on a potentially half-capacity third runway, which was different to the fully-operational runway in the consultation.
They will claim that the decision was irrational in a number of areas including the economic case, the impact on noise, air quality and public transport and the approach to climate change issues, and that Mr Hoon failed to provide adequate reasons for his decision.
If permission is granted it is unlikely that a hearing will take place until the early part of 2010.
Hillingdon Council leader Ray Puddifoot, speaking on behalf of 2M, said: "The number of organisations backing this challenge is unprecedented. It shows that just about everyone other than Geoff Hoon thinks the Government has got this wrong.
"For the local authorities the real concern is that the Government has not proved that a third runway can be operated without breaching air pollution limits, making noise worse or creating intolerable congestion on local roads and public transport."
It is expected that papers will be served and a full case will follow at some point in the future.
