Heathrow today cited growth in cargo volumes as making expansion of the airport “mission critical” for the next prime minister.

This came as the airport declared that new polling revealed “overwhelming” Parliamentary support for an expanded Heathrow, with more than two-thirds of MPs backing a third runway.

Cargo volumes rose 2.1% in June but passenger numbers declined by 1% year-on-year to 6.6 million, partly due to bad weather cancellations and recurring French air traffic control strikes.

Larger, quieter aircraft continued to be a driver for growth in passenger volumes which are up 0.6% for 2016 so far as airlines deploy new Airbus A380 superjumbos and a record number of Boeing 787 Dreamliners at Heathrow.

Heathrow chief executive John Holland-Kaye said: “With cargo volumes at Heathrow growing, our next prime minister has a real opportunity to secure Britain’s legacy as an outward-looking trading nation.

“Now more than ever, a decision on Heathrow expansion must be at the top of her in-tray.

“We’ll double cargo capacity at the UK’s largest port, helping even more British exporters trade with all the growing markets of the world.

“And at a time of uncertainty, a £16 billion privately funded infrastructure investment will create jobs and growth across the UK.

“And with Parliament overwhelmingly endorsing a third runway, our next prime minister can send the strongest possible signal that Brexit Britain is open for business and confident in its future by expanding Heathrow.”