The leader of Medway council has expressed alarm over attempts by Boris Johnson to resurrect the possibility of a new airport in the Thames Estuary, just 18 months after the idea was rejected by the government-appointed Davies Commission.

The Mayor of London's desire for a four-runway hub on the Isle of Grain was ruled out in September 2014, but his office has now published a report claiming it is one of the only ways to secure the new routes required to boost the UK economy.

But the idea drew short shrift from Cllr Alan Jarrett (Con), who said the Mayor should drop the idea.

"Boris never gives up. It does give me concern and that is why we allocated money to lobbyists to keep an eye on this sort of thing. It does not surprise me. It could be part of his leadership campaign but if it is, he's not going to get much support from MPs if he thinks he can trash Kent," he said.

Mr Johnson believes a hub in the Estuary or an expanded Stansted would offer around double the number of long haul and domestic routes served by Heathrow, while also exposing 95% less people to aircraft noise.

He said: "If we are to secure the connectivity we need to support our future growth and prosperity - and do so without dire impacts on public health - then we must do better than Heathrow.

"If we are to secure the connectivity we need to support our future growth and prosperity then we must do better than Heathrow - Boris Johnson

"We need a long-term vision for the right airport that sustains our economy and safeguards our public health. I would urge Government not to turn its back on our future."

The report produced by Mr Johnson's office, a 78-page document titled Landing The Right Airport, says a new hub would serve 114 daily long haul routes by 2050, compared with 75 at Heathrow.

An airport in the Isle of Grain could cost up to £25bn, compared to £18.6bn for an extra runway at Heathrow.

Speaking to the Press Association, Mr Johnson's chief aviation adviser, Daniel Moylan said a new airport cannot be ruled out.

"The likelihood of closing down Heathrow - and these arguments will help in doing that - is quite high," he said.

"After that, everything is up for grabs."

Mr Johnson's latest case for a new airport comes after Medway councillors agreed to put aside cash to continue their fight against the proposal should the need arise.