"London doesn't need another hub airport - the capital already has more flights to the world's main business destinations than our European neighbours. David Cameron's pledge to lead the greenest Government ever will ring hollow if he gives the green light to a huge expansion in air travel."
Architect Lord Foster has already produced plans for a £50 billion (NZ$96.3b) airport on the Isle of Grain in Kent, which has been backed by Johnson. The plan envisages a 24-hour, four-runway airport, with each runway 4km long and with facilities to cope with 150 million passengers a year.
The scheme is backed by business groups and the airline industry.
Simon Buck, chief executive of the British Air Transport Association, said: "The Government needs to maintain and build UK connectivity to emerging markets through permitting privately funded additional extra airport capacity where it is most needed and demand is greatest - in the southeast."
But Protect Kent, which promotes the diversity of rural England, argued that the airport would have a disastrous impact on land both north and south of the Thames.
Leaders on Medway Council called on the Transport Secretary to attend a meeting and hear their objections. The council's four group leaders said that 76 per cent of the British public were opposed to the airport.
"If it were to go ahead, it would have a huge effect on the lives of hundreds of thousands of residents in Medway, as well as across Kent and the wider Thames estuary, and would devastate an area of global environmental significance."
An airport would cost up to £70 billion, would require huge highways and infrastructure and would cut great swathes off the green belt and countryside, the council's leaders say.
But Johnson said he believed the tide of opinion was changing in favour of a new airport: "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. We are now being left badly behind."
Downing Street said that the Government had made clear in last November's Autumn Statement that it was ready to "explore all the options for maintaining Britain's aviation hub status, with the exception of a third runway at Heathrow".
- INDEPENDENT