David Cameron was expected to approve the £17.6bn expansion next month, with the announcement followed swiftly by a Commons vote. However, that timetable is in doubt because of the prime minister’s resignation and the possibility his replacement will be Boris Johnson, a staunch runway opponent.

Heathrow’s chief executive, John ­Holland-Kaye, claimed the Brexit vote had strengthened the case for expansion at the airport: “At an uncertain time for the British economy, MPs recognise that Heathrow is a private-sector infrastructure project that will spread growth across Britain from the moment that we get a green light.

“Now more than ever, people across Britain are counting on the government to take bold decisions that show we are a confident outward-looking trading nation.”

Holland-Kaye cited a survey of 150 MPs commissioned by the west London hub that found about two-thirds believed the project would strengthen the UK economy. MPs also ranked Heathrow expansion as the most important infrastructure project for spreading growth across the country, according to the airport.

But campaigners against airport expansion claimed the fallout of the EU ­referendum could delay a decision being made on Heathrow. It had previously been suggested ministers could announce whether Heathrow or Gatwick should be expanded before the parliamentary break at the end of July.

John Stewart, chairman of the anti-Heathrow expansion group Hacan, said Cameron’s resignation could mean a further delay. “Brexit must cast doubts on whether a third runway at Heathrow will ever be given the green light,” he said.

“The prime minister and the chancellor have lost the fight of their lives. Outers like Boris Johnson, who is fiercely opposed to Heathrow expansion, have won. At the very least, a decision on a new runway must now be up in the air.”

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