Pressure is mounting on the government to back London’s new airport hub in the Thames Gateway area.

The plan – strongly opposed by Medway and Kent councils – has been pitched back into the headlines by its biggest supporter, the Mayor of London Boris Johnson.

The mayor has now said the situation is becoming critical. It followed an announcement by Willie Walsh, the chief executive of British Airways, that his airline was now looking to expand in Madrid because there was nowhere suitable in Britain

A few years ago, government officials proposed a six runway airport should be built on the Hoo peninsula. It would have destroyed all the countryside from Hoo to Grain north of the A228, but conserved the power stations on the Medway shore.

That was defeated after worldwide environmental objections raised by the RSPB.

Mr Johnson’s plan is for an artificial island in the estuary using high speed train services to get passengers to and from the planes.

He told The Times CEO Summit the airport would be the "single biggest and boldest step" the country could make to ensure London remained a major city.

Mr Johnson added: "The question is whether, as a country, we have the guts to do something this big and bold – and deal with the issues of those who live in Kent and Essex."

The third runway plan for Heathrow was thrown out by the new government last year.

Mr Johnson was reported to have said: "You can’t expect Londoners to put up with the noise."

His campaign is supported by the Murdoch-owned Times which ran a strongly-worded editorial backing the idea. Today, Tuesday, its lead story is about congestion over Heathrow.

The pressure on local air space has mounted with another major carrier, EasyJet, announcing it will operate 10 routes from Southend airport from next April using locally-based jets.

They are also expected to provide fast rail links from the airport to London for visitors to the Olympics.

The Times said Mr Johnson has thrown down the gauntlet to David Cameron and George Osborne because the challenge was a political one, not a financial one.

Heathrow last year averaged 1,231 flights every day on its two runways.

Cllr Rodney Chambers, Medway Council leader, said the country could not afford a £70 billion airport, adding: "It would cause untold environmental damage as well as noise and air pollution."