London: Britain will decide whether to proceed with a £23 billion ($36 billion; Dh132.8 billion) plan for a third runway at Heathrow Airport by the end of the year, Prime Minister David Cameron said on Wednesday, setting up six months of political skirmishes over the issue.

Lawmakers broadly agree that the London area needs a new runway to remain economically competitive but its location has been disputed for over 25 years. Proposals to expand Heathrow in densely populated west London are politically divisive and likely to fuel tensions in the ruling Conservative party.

Cameron set the deadline after a government-appointed commission selected Heathrow, Britain’s busiest airport, as the preferred location for expansion, following a three-year study.

“A decision will made before the end of the year,” Cameron told parliament. “It is important, now that there is a very detailed report, that we study and are very clear about the legal position. If we say anything now before studying the report, we will endanger whatever decision is made.”

Should he back a new runway at Heathrow, it would represent a U-turn for Cameron, who when in opposition in 2009 said that would not happen under his watch, “no ifs, no buts”.

The commission’s recommendation was accompanied by measures to limit the noise and environmental impact of a new runway.

A previous expansion plan for Heathrow was scrapped in 2010.

The new proposal was described by the Airports Commission as “fundamentally different”, citing accompanying conditions to ban night flights and introduce a noise levy.

The Heathrow runway plan beat two other shortlisted options, another at Heathrow and one at the country’s second largest airport Gatwick. It offered the best way to add “urgently required” long-haul routes to new markets and would provide the most benefits to the wider economy, the commission said.

Mayor Johnson speaks out

A number of high-profile Conservative politicians, including Mayor of London Boris Johnson, have long-opposed an additional runway at Heathrow.

Launching an impassioned attack on the Heathrow proposal, Johnson, widely seen as a potential successor to Cameron, said it would face legal challenges.

“This highly predictable report offers a short-termist recommendation that would be judicially reviewed from here to Kingdom come and is completely politically undeliverable,” he said.

Johnson favours an alternative plan to build an entirely new airport in the Thames Estuary east of the capital.

But businesses and airlines largely favour the expansion of Heathrow, which is operating at 98 per cent capacity.

Britain, whose aviation sector represents 2.1 per cent of its economy, is losing ground to rival airports.

The fast-growing Dubai hub overtook Heathrow last year as the world’s busiest airport for international passenger traffic, while in Europe, Heathrow’s two runways compare to the four at Charles de Gaulle in Paris and six at Amsterdam’s Schiphol.

Davies urged the government to act to protect Britain’s reputation as an open economy.

“As we’ve gone around the world we’ve found that it’s become a rather symbolic point,” he told the BBC. “Is London prepared to make the decisions it needs to become a global city?” The report estimated that the new runway would cost £17.6 billion plus £5 billion in additional access costs. The new runway could add 260,000 flights a year to Heathrow, compared to the 470,000 movements currently and against the 425,000 flights in and out of Schiphol annually.

Heathrow has said that between its shareholders and the credit markets, it will be able to fund the new runway but it would expect the government to help with road improvement costs.

Heathrow’s largest shareholder is Spanish infrastructure firm Ferrovial. Other partners include Qatar Holding, China Investment Corp and the Government of Singapore Investment Corp.

The commission estimates that the new runway at Heathrow could be delivered by 2026.

Gatwick, south of London, which is run by investment group Global Infrastructure Partners and whose other shareholders include Abu Dhabi Investment Authority, National Pension Service of Korea, California Public Employees’ Retirement System and the Future Fund of Australia, believed it was still in the race.

“We are confident that when the government makes that decision they will choose Gatwick as the only deliverable option,” Gatwick CEO Stewart Wingate said.