New transport secretary Chris Grayling has pledged that the government will to “move rapidly” to make a decision on a new runway in the south-east.

Grayling, who was appointed to the role in Theresa May’s cabinet reshuffle, said that an immediate decision would be taken to “provide certainty” to businesses.

It is thought that a ruling could be made in early September, after parliament returns from the summer recess.

The latest development came after London mayor Sadiq Khan gave his backing to expansion at Gatwick over rival Heathrow.

“The new Prime Minister has a very important decision to make regarding new airport capacity, and I urge her to rule as swiftly as possible in favour of a second runway at Gatwick, which would bring substantial economic benefits,” he said.

Former transport secretary Patrick McLoughlin said last month that a final decision on airport expansion was unlikely to be taken before October.

The Airports Commission made an overwhelming recommendation a year ago in favour of a third runway at Heathrow, saying it would create greater economic benefits and enable more long-haul routes than a second runway at Gatwick.

But a decision on the issue has been delayed three times in the past year. This includes one delay to allow for further assessment of the environmental and noise impact of more flights.

Grayling, interviewed on BBC Radio 4’s The World This Weekend said: “I am very clear that I want to move rapidly with a decision on what happens on airport capacity. It is a decision that will be taken collectively by the government.

“We have a quasi-judicial role so I’m not going to say today whether I prefer Gatwick or Heathrow. There’s two options at Heathrow. I’m going to look at this very carefully in the coming weeks.”

Expansion of Heathrow may face opposition in the new cabinet, which features hardline critics in Boris Johnson and Justine Greening — while Theresa May repeatedly criticised previous attempts to build a third runway there while in opposition in the late 2000s.

Given the strength of feeling on the issue, it is unlikely that a decision will be taken during the parliamentary summer recess, The Times reported.

MPs start their summer break on Thursday and return on September 5.