A proposal to build a major airport on the Hoo peninsula in north Kent is one of several options being considered by the Mayor of London, Boris Johnson.
Mr Johnson wants to increase flight capacity around London without expanding Heathrow.
He has also been considering building an airport in the Thames Estuary.
A spokesperson for the Mayor said it was vital that a location for extra runway capacity was found for London to remain one of the leading world cities.
In 2002, a new airport at Cliffe on the Hoo peninsula was one of several options being considered by the government for airport expansion in the South East.
However, in December 2003, the government decided to leave Cliffe out of its airport expansion plans.
The latest proposal for the Hoo peninsula has been put forward by John Olsen, the British former head of Cathay Pacific.
The site is renowned for its populations of wintering birds, while in summer it is an important breeding ground for birds such as avocets, marsh harriers, Mediterranean gulls and little terns.
In a statement on Sunday, Mr Johnson's spokesperson said: "The Mayor has kickstarted a debate about the best way to increase airport capacity in and around London and every extra contribution to that discussion is welcome.
"The Deputy Chairman of Transport for London, Daniel Moylan, is working on a review that will certainly take Mr Olsen's proposal into account.
"But whatever conclusion is eventually reached it is vital that a location for extra runway capacity is found for London to remain one of the leading world cities."
Paul Clark, former Labour MP for Gillingham and Rainham, in north Kent, described the proposal as "absolute madness".
"The government back in 2002/2003 went through a big exercise of commissioning numerous reports to look at how we coped with the expansion of air demand in the South East," he said.
"One of those proposals was exactly this one that seems to have resurrected itself out on Cliffe.
"The costs involved, let alone environmentally the damage that is done, and the threat that it would give to the safety of passengers through bird strike and so on, makes it a very dangerous plan to proceed with."
Mr Clark urged the government to "do a U-turn" and accept that Heathrow "is really the only practical solution to expanding our hub airport... to accommodate the demands of both business and pleasure aviation requirements in the future".