Thames Estuary airport poses 'considerable risk' to taxpayer
An airport in the Thames Estuary would present a "considerable cost and risk to the taxpayer", according to reports published by the Airports Commission.
An estuary airport on the Isle of Grain has been proposed by London Mayor Boris Johnson.
Four studies into the feasibility of the airport have been published.
They state airlines and passengers believe the scheme would carry "significantly more risk than opportunity".
One of the reports also stated that explosives on a sunken World War Two munitions ship in the estuary, the SS Richard Montgomery, would need to be removed or treated before the airport could be constructed.
It added: "Full containment or removal are deemed high-risk and high-cost options, potentially requiring evacuation of the local area for a period of many weeks or months."
The Airports Commission has been tasked with examining the need for additional UK airport capacity. It has shortlisted three options, which include adding a third runway at Heathrow, lengthening an existing runway there, and a new runway at Gatwick.
However, the commission, led by businessman Sir Howard Davies, will also consider a new airport in the Isle of Grain.
The three latest reports looked at operational feasibility and attitudes towards the airport, socio-economic impacts and surface access.
The first report, which looked into the environmental impact of the airport, said it could cost up to £2bn to provide alternative habitats for wildlife if the airport was built.
One of the reports states that Heathrow would have to be closed for a new hub airport in the Thames to open.
It states: "Overall, the challenges to transition are considerable and amount to a significant cost and risk to the taxpayer in terms of commercial negotiations, infrastructure development and potential failure."
Daniel Moylan, who is the mayor of London's chief adviser on aviation, said: "Our team will now analyse these reports in detail but it appears they confirm the huge benefits to the country's prosperity that would flow from moving Heathrow to a new location and prove that there are challenges, but no showstoppers, to achieving that.
"The case studies of how this has been successfully done in other countries are particularly valuable.
"Of course there are risks, but all the proposals being considered by the commission carry risk.
"The Airports Commission can have no alternative but to include the estuary option on its formal shortlist."