In a letter, Sadiq Khan claimed that expanding Heathrow Airport instead of Gatwick could worsen London’s already poor air quality.

“A second runway at Gatwick will bring substantial economic benefits to London and the UK in terms of jobs, growth and investment, without the significant environmental cost to Londoners of expanding Heathrow.

“Heathrow is currently an air pollution hotspot and will be for years to come even without expansion, unless significant mitigating measures are put in place.

“Aviation expansion in the South East must not be at a further cost to Londoners’ health and wellbeing, and increased noise pollution is also a significant factor in my opposition to Heathrow expansion.

“This is a vital decision for London and the UK and we must get it right.”

Mr Khan also stated that building a second runway at Gatwick would show the world that London was open for business and enable the capital to keep competing with other major cities. 

“London’s economy needs additional aviation capacity in order to stay competitive with other major global cities and an early decision from you would show to the world that we are open for business.

“Gatwick is the most viable option presented by the Airports Commission.” 

Last month, Mr Khan visited Gatwick Airport to praise plans for an additional £200m investment over the next five years.

In July 2015, experts argued that the new Heathrow runway plans would boost demand for commercial property and provide long-term security for developers in west London.