LONDON Mayor Boris Johnson has urged the commission deciding on future airport capacity not to sideline a Thames Estuary airport plan.

The Whitehall-appointed Airports Commission announced last month it had shortlisted for further study new runway options at Heathrow or Gatwick.

Led by former Financial Services Authority chief Sir Howard Davies, the commission did not shortlist any of the Thames Estuary airport plans – schemes which are supported by Mr Johnson. But the commission left the door open by saying it would look further at one of the estuary schemes, for a new airport on the Isle of Grain.

Mr Johnson has written to Sir Howard expressing concern that assessment of the Isle of Grain plan could fall behind that of Heathrow and Gatwick.

The letter said: “Such a delay would place a severe disadvantage on the Isle of Grain proposal and imposing it would give the impression you had prejudged the findings of the additional work on an Isle of Grain option before it had even begun.”

Sir Howard and his team are due to produce their final report on airport capacity in the summer of 2015 – after the next general election.

Launching the commission’s interim report last month, Sir Howard said the estuary airport plan could cost as much £112 billion – much more than either the Heathrow or Gatwick options.

He also said the construction challenge in building a new estuary airport would be “massive”.

Mr Johnson is vehemently opposed to the expansion of Heathrow. An extra, third runway at Heathrow was given the goahead by the Labour government in 2009, but scrapped by the coalition Government when it took power in May 2010.