LONDON (REUTERS) - A plan to build a major new airport to the east of London was rejected by a government-appointed commission on Tuesday, dealing a blow to its high-profile backer, the city's mayor Boris Johnson.

The Airports Commission said the idea of building a costly new airport in the Thames Estuary, nicknamed Boris Island, had not made the shortlist of options it is considering to expand Britain's runway capacity.

It will now make a final recommendation by summer 2015 from three remaining options, including two plans to expand Heathrow Airport and one to expand Gatwick Airport.

British politicians and business leaders agree the south east of the country needs a new runway but the idea of adding greater capacity near to London is unpopular with many voters because of noise, pollution and safety concerns.

Johnson, who is seen as a potential successor to Prime Minister David Cameron, confirmed last week he would try to run for parliament next year in a west London constituency, bringing his long-held opposition to expanding nearby Heathrow into the political spotlight.

Heathrow, which by passenger traffic is Britain's busiest airport and the third busiest in the world, is already running at 98 per cent full. The airport says this means it is falling behind rival European hubs in the battle for lucrative routes to emerging markets.

Instead of expanding Heathrow or Gatwick, Johnson threw his weight behind building a new airport to the east of the city.

However, the Commission said last year the project would cost up to 112 billion pounds (S$184 billion), or around five times as much as the other three shortlisted options.

Johnson said in a statement that he was dismayed by the decision, and would continue to fight for the project.