Plans for an island airport off the north Kent coast to replace Heathrow have been slammed by the leader of Kent County Council.

Cllr Paul Carter (Con) said the proposal for an airport off Sheppey, mooted by London Mayor Boris Johnson, was a non-starter and that developing Manston airport in Thanet was the way to address the issue of capacity.

"It is the wrong idea in the wrong place. There is a massive opportunity at Manston, which could deal with between six and seven million passengers - enough, I believe, to deliver the kind of capacity will be needed with the plateau in air travel I suggest is likely."

He denied the location of Thanet’s Kent International Airport militated against its development as a significant regional airport, saying the prospect of high-speed domestic rail services along the Channel Tunnel rail link, along with a third Thames crossing, would provide the necessary ‘connectivity’.

"We have a major opportunity to bring to the east Kent economy an aviation business that could really take off and really open up the area to investment."

He did not accept Thanet was too remote a location and took too long to reach to make it viable. "It can take you a significant amount of time to get to any of the airports we have," he said.

Meanwhile, the idea of a Sheppey airport was also condemned by the opposition Labour group at County Hall. Party spokesman Cllr Roger Truelove, a Swale councillor, said: "This is a barmy idea and only put forward to placate the voters of West London who are opposed to the growth of Heathrow. Johnson is clearly putting London First, and shows a complacent disregard for Kent. He will know from the work done on the Cliffe Airport proposal several years ago that a new London airport in Kent is a non-starter. The costs then were far too high and airlines indicated they would not use such a site."

Mayor Johnson said: "If you look at what is going on in other countries around the world –in Hong Kong, in Washington – it’s not impossible to move the capital’s biggest airport."