Airport would be built over this countryside

All the options are likely to bring protests from environmentalists, but business and tourism groups say failure to meet demand would damage the economy.

The site at Cliffe, on the Kent side of the Thames Estuary, would attract fierce criticism from cultural groups as well as environmentalists.

It is close to a cemetery that inspired a scene in Charles Dickens' Great Expectations.

The Thames is also regarded as one of Europe's most important estuaries by the Royal Society for the Protection of Birds (RSPB).

It would be the worst development we have seen ever

RSPB spokesman Paul Outhwaite

But supporters of the Cliffe site say it would allow 24-hour flying because there would be less of a noise problem and would involve demolishing few homes.

There are also potentially good rail links with the Channel Tunnel line and London stations.

The Financial Times' political editor, Brian Groom, told BBC Radio Kent there are plenty of barriers to the project.

Possible options

"The infrastructure problems are very considerable - we have to build the airport itself, build homes for people who are going to work there, and still have to build a rail link into these rail links.

"Whether any of these rail links can take the kind of volume we are talking about is another matter."

Kent councillors are in favour of extending the existing airfield at Manston, a former RAF site.

Work has already started to pave the way for passenger flights and it can already take flights from New York.

Rodney Chambers, leader of Medway Council, said: "If improvements were made in rail and road communications between London and Manston, that would be the appropriate place to go as it has both the site and the runway."

Mr Byers is considering several options

The Department of Transport has refused to confirm if Cliffe is one of the proposals being considered and said no decisions about new airport capacity had been taken.

A spokesperson said: "The Secretary of State has been considering how to respond to the demand for air travel over the next 30 years and will be issuing a consultation document on the possible options in the spring.

"The responses to the consultation will feed into the aviation White Paper due later this year."

The latest airport speculation comes just months after the government gave the go-ahead for a fifth terminal at Heathrow.