Campaigners fighting the expansion of Heathrow Airport have threatened legal action over an “unfair” air quality consultation by the government.
The Teddington Action Group said it was considering launching a judicial review over the Airports Commission’s work.
It said there had been a “lack of proper engagement” over the consultation.
The group also claim there could be a conflict of interest after the chairman of the commission accepted a new role.
However the Airports Commission said Sir Howard Davies would not take up his role at RBS, which works with the owners of Heathrow and Gatwick, until the commission had concluded.
The commission gave people three weeks to submit further evidence about air pollution on 8 May, but campaigners argue this was shorter than the consultation time usually recommended by the government.
The Teddington Action Group also claims the period was insufficient for people to read the report’s 200 pages of technical data.
Spokesman Paul McGuinness said: “The lack of proper engagement by the Commission in relation to the latest air quality consultation is unacceptable and local people should be consulted in a meaningful way on an issue that directly impacts their health and wellbeing.”
The Airports Commission is expected to publish its final report this summer
The group also alleges there could be a potential conflict of interest with commission chairman Sir Howard Davies also acting as chairman of the Royal Bank of Scotland which works with companies that own Gatwick and Heathrow airports.
The campaigners said they intended to take legal action unless another consultation on air quality is conducted and Sir Howard stands down from his role with the Airports Commission.
In a statement, the Airports Commission said Sir Howard would not take up his role at RBS until September, after his work at the Airports Commission has concluded.
The statement added: “In the interim period, there are procedures in place to ensure that Sir Howard will have no knowledge of or involvement in RBS’s work in the aviation sector before the Commission’s Final Report is published.