A proposed second runway at Gatwick would destroy ancient woodland, campaigners have claimed.
The Woodland Trust believes each of the three plans put forward by the airport would “obliterate” a large amount of “irreplaceable habitat”.
Mole Valley Council has also queried some of the predicted economic benefits the new runway would bring to the area.
Gatwick said its proposals are still being developed and the public consultation continues.
The airport had previously suggested that building a new runway at Gatwick would be less damaging to the environment than expanding Heathrow.
But the Woodland Trust has dismissed this claim, believing up to 19 acres of woodland would be destroyed, the BBC reported.
Campaigner Katharine Rist said: “Ancient woodland is an irreplaceable habitat – therefore it should not be lost to development.”
However, she said the trust was also against adding a runway at Heathrow as that would lead to the destruction of ancient trees around the site.
Francis Maude, the MP for Horsham, has also declared he is against the second Gatwick runway because of the environmental impact on the area.
Meanwhile, Mole Valley District Council has expressed concerns about how much the proposals will benefit local communities.
The local council has questioned the accuracy of Gatwick’s growth forecasts.
Gatwick has claimed a second runway would create 120,000 jobs in the area by 2050, but the council believes predictions have lacked clarity.
Both Gatwick and Heathrow have submitted expansion plans to the government’s Airports Commission.
A 12-week consultation on Gatwick’s proposals will finish on August 15.