London Mayor Boris Johnson has renewed his support for a Thames estuary airport with a call to the Prime Minister to stop “pussyfooting around” over major infrastructure projects.

In comments that indicate he intends to continue to press the case for a new hub, Mr Johnson said there was inertia in the government but Chancellor George Osborne backed the plan and Transport Secretary Justine Greening “got” the need for an airport.

The mayor, who some believe may eventually seek to return to Westminster as an MP, made his comments in an interview last week.

They will irritate opponents of the scheme for a new four-runway estuary airport who believe it would be too costly, environmentally damaging and unlikely to be supported by airlines.

Mr Johnson also criticised the government’s decision to delay the publication of a consultation into Britain’s airports until after the next election as “totally mad”. He added: “I don’t think you can rely on Heathrow.

“Even if the government was so mad and wrong to do the third runway or mixed mode [mixing take-offs and landings on the same runways], those solutions would rapidly run out of usefulness and time.”

Mr Johnson said the Chancellor was “very much up for” big infrastructure projects such as an airport in the Thames estuary.

However,Mr Johnson claimed that David Cameron has yet to be convinced and blamed the “institutional inertia of the government”.

The KM Group revealed in February how Mr Osborne and his officials had held a string of private meetings with the backers of plans for a new airport in Kent, including Mr Johnson.

The previously undisclosed contacts stretched over a four-month period between May and August last year, according to details obtained by the KM Group under the Freedom of Information Act.

Plans for an airport near Sheppey in the Thames estuary have been talked about for decades.

The latest instalment of the saga involves two proposals – the Lord Foster plan and Boris Island.

Architect Lord Foster drew up plans last year for a super hub on the Isle of Grain with aircraft flying in and out over the estuary. It would have high-speed train links to London and the Continent, with a potential super station near Sittingbourne.

Boris Island would see a man-made stretch of land built in the estuary about two miles off Sheppey with transport links reaching over to Leysdown and beyond.

Both plans, which would cost more than £40 billion, are controversial but are seen by many Londoners as an ideal alternative to expanding Heathrow.

Another proposal, favoured by Kent County Council, is to look at Manston Airport near Ramsgate. The former RAF station would provide close links to the European mainland and could be linked to London by a high-speed rail line.

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