The London Mayor previously called for an airport to be built on man-made islands in the Thames Estuary, near Whitstable.

Foster + Partners and consultants Halcrow have nbow come up with a new plan after collaborating on a self-funded £100,000 study to produce a detailed vision for a Heathrow replacement airport to be called The Thames Hub.

Details of the plan, which could cost £40bn – £50bn, are due to be unveiled next month.

The airport hub plan would bring together rail freight connections between the UK’s main sea ports. At its centre would be a 150 million passenger airport powered by a tidal energy barrage and a new flood protection barrier.

Johnson said: “I am grateful to Lord Foster for spelling out the potential for a new airport, properly rooted in a broader vision for the Thames estuary, where it would make a vital contribution to economic growth.

“I believe this is vital not only so London remains in the premier league of aviation, but also to generate jobs and opportunities for decades.”

Lord Foster said: “These visionary proposals are far from future fantasy. They are both essential and down to earth.

“When you look at the eastwards thrust of London’s infrastructure, with the Channel Tunnel and the Olympics, you can see how it would be possible to create a 24-hour airport.

He said: “This move would greatly improve the quality of life for Londoners by reducing pollution and improving security. It would also allow London to compete with rapidly expanding airports in Europe and the Middle East.

“The arguments are extraordinarily persuasive and the precedents are also compelling. More than 10 years ago Hong Kong built what was then the world’s largest airport at Chek Lap Kok, an island reclaimed from the sea – in just four years.”

Halcrow group board director, David Kerr said: “The Thames Hub would provide a major economic boost for Kent and Essex, with the creation of hundreds of thousands of jobs over a number of years and provide noise and air pollution relief for London’s population.

“The proposals would make a significant contribution to the UK’s commitment to reduce carbon emissions. If the UK is to remain globally competitive, these proposals need to be seriously considered.”