New Runway at Heathrow "Will Fail on Every Level", Says London Mayor

London's mayor, a potential successor to British Prime Minister David Cameron, said a proposal to build a third runway at Heathrow Airport was doomed to fail, complicating an already fraught issue for the government.

In July, after a three-year study, the Airports Commission recommended Heathrow as the best option for an additional runway over two other shortlisted airports, arguing this offered Britain the best way of adding long-haul routes to new markets that it said were "urgently required".

But Boris Johnson, a long-standing critic of the plans, said on Monday the report itself showed that the proposal would not solve capacity issues.

"The figures teased out of their report on the fall in domestic and even long-haul connectivity show that as a nation, by expanding Heathrow, we would merely be investing in decline," he said in a statement.

"Their report very clearly shows that a third runway will fail both London and the UK on every level."

Johnson, who re-entered parliament at national elections in May, has sent a dossier to lawmakers pulling apart the report's recommendations, according to a statement from his office. He raised questions over noise pollution data and the number of night flights, both key concerns for residents living under flight paths.

He instead suggested building a new airport in the Thames Estuary to the east of London, a proposal known colloquially in Britain as "Boris Island".

Cameron said in July that he would make a final decision on the 23 billion pound plan by the end of the year but the government is likely to anger supporters with whatever choice it makes.

The prime minister is in a difficult spot after pledging to voters before the 2010 election that first brought him to power that he would not allow a third runway at Heathrow, "no ifs, no buts".

Johnson is one of several high-profile Conservative lawmakers who oppose the move and is tipped by many in the press to succeed Cameron, who has ruled out serving a third term as prime minister.

Heathrow's largest shareholder is Spanish infrastructure firm Ferrovial.