A new London airport in the Thames Estuary could take as little as six years to complete and would not cost the taxpayer a penny, the capital’s mayor Boris Johnson claims.

He believes the so-called Boris island project would not take “decades” to build and compared the construction of the £50 billion scheme on a man-made island to both Hong Kong and Singapore’s airports.

Johnson told the Daily Telegraph that as long as there was “political will and energy” the site could be operational in a very short space of time. Hong Kong airport took just six years to build at a cost of $20 billion.

“Decades is not necessarily the case,” he said. “If you look at what was achieved in Singapore and Hong Kong, you saw the creation of airports very, very rapidly indeed. It is possible with political will and energy to do it in a very short space of time. There’s no reason why you shouldn’t do something in that kind of time scale.”

He suggested that there were sovereign wealth funds around the world who would be prepared to pay for the project. But additional infrastructure links such as rail would have to met by the taxpayer.

Mr Johnson said any further development of Heathrow would cause “massive congestion in west London” as it was “fundamentally in the wrong place”.

A Department for Transport spokesman told the newspaper: “No decisions have been taken. As the Chancellor made clear in his autumn statement, we will explore all the options for maintaining the UK’s aviation hub status with the exception of a third runway at Heathrow.

“The government will consult on a sustainable framework for UK aviation this spring, at which time we will set out our long-term plans for the sector.”

Reports that support for the Thames Estuary project is growing within government have recvied the backing of the travel industry, with chief executive of Flybe Jim French among those who have commented.

He said: “Flybe believes strongly that any new airport must be a national resource, guaranteeing access for all UK regions to an international hub, thereby maximising the economic potential of the whole of the UK.”