The mayor of London favours expansion at the West Sussex airport over Heathrow, saying that it would bring “substantial economic benefits”.

Theresa May will likely have to make a decision over where a new runway will be built in the coming months. A decision had been expected this summer but the turmoil caused by the referendum result meant it was delayed.

Khan’s support for Gatwick comes as the airport announced an additional £200 million worth of investment.

“Gatwick is the front door to London for millions of visitors to our city and I salute their decision to spend another £200m on improvements to the airport. They have put together a formidable plan that is a fantastic display of their confidence in London," Khan said.

“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."

Gatwick Airport chief executive Stewart Wingate said: “It is now clear that only Gatwick can deliver the runway Britain needs to boost international competitiveness and trading links at a time when it is most needed, and we can do that before 2025.

“This investment will also make sure that we can continue Gatwick’s record growth and transformation. Our total investment since coming into private ownership now stands at £2.5 billion as we operate the World’s most efficient single runway airport.”