London mayor Boris Johnson's plans for a new airport in the Thames estuary were today dismissed by the government's independent commission on aviation.
The decision leaves the Airports Commission with three remaining options — a third runway at Heathrow, extending an existing runway at Heathrow, or a second runway at Gatwick.
Johnson's proposal for a new four-runway hub on the Isle of Grain to the east of London would have likely cost more than £100 billion.
How it might have looked: An architect's illustration of the proposed "Boris Island" airport
Critics had said this high price tag made "Boris Island" economically unviable and that the mayor's plan was a "vanity project".
Commission chairman Sir Howard Davies said the proposal was too expensive and would prove disruptive, both economically and for the environment.
He said in the report: "We are not persuaded that a very large airport in the Thames estuary is the right answer to London's and the UK's connectivity needs.
"While we recognise the need for a hub airport, we believe this should be a part of an effective system of competing airports to meet the needs of a widely spread and diverse market like London's.
"There are serious doubts about the delivery and operation of a very large hub airport in the estuary. The economic disruption would be huge and there are environmental hurdles which it may prove impossible, or very time-consuming to surmount."
But Johnson today claimed the commission had "set back the debate by half a century".
He said: "Gatwick is not a long-term solution and Howard Davies must explain to the people of London how he can possibly envisage that an expansion of Heathrow, which would create unbelievable levels of noise, blight and pollution, is a better idea than a new airport to the east of London that he himself admits is visionary, and which would create the jobs and growth this country needs to remain competitive."
The commission will make its final recommendation in summer 2015 after the next general election.
At the end of last year, the commission shortlisted the Gatwick and both LHR options (see news, December 2013). It did not shortlist Johnson's Isle of Grain proposal, but added it as a "possible consideration" after the mayor protested its absence.