Boris Johnson visited the site of his proposed Thames Estuary airport and said it reaffirmed the controversial idea as an option in his mind.

The London mayor took a boat trip on Friday looking at an area, two miles north of Sheerness, with Doug Oakervee, who is working on a feasibility study for the airport, and Labour MP Nick Raynsford, chair of a cross-party parliamentary group on the proposal.

After the visit, Mr Johnson urged politicians to seriously consider the plan.

He said: "Today’s trip has reaffirmed in my mind that a new airport in the Thames Estuary has got to be factored in as an option for London’s long-term aviation needs.

"I am reassured by a number of aspects of this visit and will now eagerly await Doug Oakervee’s initial feasibility study."

Mr Oakervee said: "I'm encouraged - from an engineering perspective it is quite clear the mayor’s ambitions could be realised.

"There is a remote site where an airport could be built with minimal disruption to people of Essex and Kent."

Opponents of the plan for the £40billion international airport claim it would have a devastating environmental impact on north Kent, including the Medway Towns.

They were given a glimmer of hope the scheme would be ditched with the announcement that a third runway at Heathrow has been given the thumbs up.

The location for the estuary airport, dubbed Boris Island, is near the wreck of the SS Richard Montgomery which sank off the coast of Sheerness in 1944 carrying a cargo of munitions.

The feasibility report is expected to be completed around the end of March.