British Prime Minister David Cameron is “interested” in building a new airport in the Thames Estuary to keep London’s position as a global hub aloft, the city’s mayor said yesterday.

The government will reportedly announce a consultation within weeks on the idea, dubbed “Boris Island” after it was first proposed by Mayor of London Boris Johnson, a colourful figure known for his flights of rhetoric.

“I think that where we are is that the government is increasingly interested in this idea,” Johnson told BBC radio.

“George in particular and Dave understand the logic of doing something to alleviate the problem,” he added, referring to finance minister George Osborne and Prime Minister David Cameron.

London’s Heathrow airport, the world’s busiest in terms of international passenger traffic, is almost at full capacity but ministers have ruled out building a third runway because of environmental and residents’ concerns.

Passengers can also enter the capital via airports at Gatwick, London City, Stansted and Luton, but they are considered insufficient to meet demand and there are fears that British businesses will suffer.

“You can’t go on expecting Britain to compete with France and Germany and other European countries when we simply can’t supply the flights to these growth destinations – China, Latin America,” Johnson said. “We are now being left badly behind.”

Johnson, a member of Cameron’s Conservative party, has proposed the building of a new airport on an artificial island in the Thames to the less populated east of London.

Environmentalists say it is an important sanctuary for wildlife.

Heathrow’s operator BAA, which is owned by Spanish construction group Ferrovial, said a new airport could threaten Heathrow’s position and would take decades to build.

“You can’t have two hubs. You can look at various cities around the world who have tried to do that,” BAA chief executive Colin Matthew told the BBC.

“The consequences of closing Heathrow wouldn’t just be big for my company it would be big for 100,000 jobs in this part of London. It is a huge issue economically and it is a huge issue politically.”

Citing sources within Cameron’s Downing Street office, The Daily Telegraph said an announcement on the government’s aviation strategy was due in March.

Norman Foster, the British architect of Hong Kong’s main international airport which opened in 1998 on largely reclaimed land, has also put forward an airport project for the Thames Estuary.

It would have four runways and a capacity of more than 150 million passengers a year.

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