Decision is particularly difficult for PM because he unequivocally ruled out a third runway in 2010, and now faces prospect of cabinet resignations

David Cameron will resolve his dilemma on whether to back a third runway at Heathrow by the end of the year, but faces the prospect of cabinet resignations and having to rely on Labour support if the government decides in favour.

The prime minister said on Wednesday that he had yet to study the recommendations of the Davies commission, which strongly backed expansion at Heathrow.

The decision is particularly difficult for Cameron because he has previously said there would be “no ifs, no buts” about Conservative opposition to a third runway. A number of his cabinet colleagues are also implacably opposed.

Heathrow third runway recommended in report on airport capacity Read more

Labour piled pressure on him on Wednesday by indicating that it would vote in favour of expansion if Cameron made a swift decision.

The party’s acting leader, Harriet Harman, said Labour would help him vote through a new Heathrow runway rather than leave the country beholden to the interests of Tory opponents such as Boris Johnson.

She told the prime minister he was in a “holding pattern above Heathrow and Boris won’t let you land” and accused him of having already made up his mind to oppose expansion.

Cameron strongly rejected reports that he had already made a decision, cautioning people against believing a newspaper article in which an anonymous No 10 aide was quoted as saying that the prime minister would not go back on his 2009 word.

The final decision on airport capacity will be officially be taken by the transport secretary, Patrick McLoughlin. Great care is being taken to minimise the possibility of a judicial review of the decision-making process, raising the prospect of ministers being banned from commenting on it before the conclusion.

Cameron said: “I am very clear about the legal position, that if we say anything now before studying the report, actually you can endanger whatever decision is made.

“The guarantee I can give you is a decision will be made by the end of the year.”

The chancellor, George Osborne, is said to back economic arguments for expanding airport capacity in the south-east, but a large number of cabinet ministers oppose Heathrow growth. They include the development secretary, Justine Greening; the chief secretary to the Treasury, Greg Hands and the foreign secretary, Philip Hammond.

The home secretary, Theresa May, is also said to have some reservations about the effect of noise on her Maidenhead constituency.

Downing Street confirmed on Wednesday that ministers would be bound by collective responsibility in the event that the government decides in favour of Heathrow expansion, raising the prospect of resignations.

Zac Goldsmith, the leading Tory candidate for the London mayoral race, is also a high-profile opponent and has threatened to resign his seat if Heathrow expansion goes ahead. It is not clear if he would go ahead with his mayoral bid on a Conservative ticket, or stand as an independent.

Tackling Cameron on the issue in the House of Commons, he said: “There is a very strong sense that the Airports Commission began life three years or so ago with a conclusion and then spent £20m backing up that conclusion.



“You are going to have to make a decision on the back of these recommendations shortly. But what assurances can you give the million or so Londoners who stand to be affected by Heathrow expansion that you will engage with the real arguments in a way that Sir Howard Davies has not?”

The prime minister promised him that the commission’s report would be “properly studied because this really does matter”.

“If you make some precipitate decision or rule out one particular option, you will actually make the decision you would like to make impossible to achieve because of judicial review,” he said.

Facebook Twitter Pinterest Boris Johnson (centre right) and Zac Goldsmith (centre left) outside parliament in London. Photograph: Stefan Rousseau/PA

Boris Johnson, the London mayor, is also a fierce critic. He said the Davies report should be “filed vertically” andthat expansion was “never going to happen”.

With more than a dozen MPs against a third runway, Cameron would have to rely on the opposition to get any legislation through the House of Commons.

Harman clearly indicated on Wednesday that her party would support the expansion of Heathrow if it passed some key environmental tests.

As the prime minister said he had not made up his mind, Harman replied: “There’s something very different coming out of No 10. They are briefing it is not going to happen.



“It looks like the prime minister has been overruled by the member for Uxbridge. You should tell him he’s not the leader of the Tory party yet. You should tell him that. Will you stand up for Britain’s interests or will you just be bullied by Boris?”

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Her argument shows that Labour intends to frame the debate over Heathrow as a matter of national interest. The party would be able to argue that Cameron has bowed to a small group of Tories with west London constituencies if he rejects the recommendations of the independent Davies report.

Michael Dugher, the shadow transport secretary, said there was “a majority in the House of Commons willing to do the right thing for the sake of the country” and urged Cameron to make a swift decision.

Labour originally proposed Heathrow expansion while in government, but Ed Miliband was not in favour and pulled the party back from supporting a third runway.

Liz Kendall, one of the Labour leadership candidates, said: “The country has to get behind this now. The time for fudge and indecision is over. Many thousands of jobs right across the country depend on Britain maintaining an international hub airport that keeps pace with the rest of the world.

“With my leadership, Labour will be the party of jobs and work, so I will back the commission’s decision. We need to act now.”

If Cameron opts for expansion at Gatwick, he would face opposition from MPs in Surrey, but there are fewer influential ministers and MPs with constituencies in the area.

MPs with constituencies near Gatwick, known as the Gatwick Coordination Group, responded to the Airports Commission report by saying it had made “a clear decision in the national interest”, which meant the case for Gatwick expansion was “dead and buried”.

“The commission was faced with a choice between a strong business case for Heathrow and an economically weak and practically inadequate case for Gatwick: a choice between around £100bn greater national economic benefit and four times more new jobs spread across the UK flowing from Heathrow, versus Gatwick which lacks resilient surface transport infrastructure and any available local labour force to staff the airport,” they said.

“Unsurprisingly, the commission has found in favour of Heathrow, the significantly better option for Britain. The report clearly shows that Heathrow can expand whilst meeting the key economic, infrastructure and environmental tests.”