Five MPs have begun a campaign against the building of a second runway at Gatwick Airport.
The Conservative MPs, who represent Sussex, Surrey and Kent constituencies, said the scheme for the airport near Crawley would be "a disaster" for communities and the environment.
They said there was "serious local concern" at the plan.
Gatwick said it had sought to engage with communities and politicians and would continue to do so.
Reigate MP Crispin Blunt, one of the members of the newly-formed Gatwick Coordination Group, said: "If Gatwick expands in the way that's planned, it will need many tens of thousands of new people working there, and they are all going to need somewhere to live.
"The airport at the moment are providing a preposterous suggestion that these people are largely going to come from existing communities in Croydon and Brighton. Well I'm afraid that's just simply not the case."
Mr Blunt also said no new railway line had been proposed.
He said the London to Brighton commuter line was already "the busiest commuter line in the country" and at capacity.
The other four MPs behind the campaign are Sir Paul Beresford, who represents Mole Valley, Mid Sussex MP Sir Nicholas Soames, Sir John Stanley, who represents Tonbridge and Malling in Kent, and Charles Hendry, MP for Wealden.
Crawley Conservative MP Henry Smith, whose constituency includes the airport, said he was invited to join the group but declined to endorse the press release.
He said: "Whilst I think Gatwick needs to make a stronger case on how it would invest in upgrading Crawley's infrastructure if the airport were to expand, I think it premature to rule out an additional runway until the Davies Commission investigating aviation capacity has reported next year."
Gatwick has submitted three plans for a new runway to the Airports Commission.
Airport bosses have set out improved public transport plans including new train platforms, new rolling stock and improvements to junction nine on the M23, and have suggested 120,000 jobs would be created by the building of a second runway.
A statement issued by the airport said: "We believe an expanded airport at Gatwick is in both the local and national interest and look forward to working with all our stakeholders to demonstrate that."
Surrey County Council opposed the plans over concerns about the impact on the environment.