PLANS to build an airport on reclaimed land in the Thames Estuary are expected to be declared feasible by an engineering expert.

London Mayor Boris Johnson wants to see whether a new four-runway airport on two man-made islands between south Essex and north Kent could provide an alternative to the proposed third runway at Heathrow Airport.

For six months, engineer Douglas Oakervee has been working on a feasibility study for the proposal.

He will discuss his initial findings tomorrow with other experts at the Institution of Civil Engineers and submit them to Mr Johnson several weeks later.

According to a national newspaper, an unnamed source who has seen the report said the airport would cost an estimated £40billion and could be built within ten years.

The main terminal could be in Kent, and the airport could be powered by underwater turbines. The exact location of the islands, which would allow easier passage for shipping, is apparently to be decided.

The Tory leadership, the Labour Government and local MPs and councils have said they are firmly against the plans.