A new Thames Estuary airport would support 336,000 jobs and contribute £92.1 billion to the economy each year by 2050, London mayor Boris Johnson claims.
The Isle of Grain proposal would mean more than five times as many jobs than if Gatwick expanded and a third more than Heathrow.
Releasing the figures in a last-ditch bid to persuade the Airports Commission to support his proposal, Johnson said: “A new hub airport, properly planned, has the potential to reshape the economic geography of London and the whole of the southeast for decades to come.
“It would be a project of a scale we are no longer accustomed to in this country, though it has become commonplace elsewhere.
“We simply cannot afford to miss out on the opportunities a new airport would give us.”
The commission is due to make a decision on the proposal next month. Opponents have described the proposal as “environmental vandalism”.
But Johnson said the options came down to “planning for the future” or “depressing short-termism”.
Rodney Chambers, leader of Medway Council, said the location was “financially, geographically and environmentally wrong”.
“It will waste tens of billions of pounds of taxpayers’ money for a project which is on the wrong side of London for the majority of passengers,” he told the BBC.
Meanwhile, pro-Heathrow expansion campaigners reacted with alarm to the news that Johnson had added his name to a list of prospective Conservative candidates for the local Uxbridge and South Ruislip constituency at the next general election.