Heathrow spent more than £2m advertising on London’s tubes and buses in 2015, according to Mayor of London Boris Johnson.

It spent £256,854 on advertising on Transport for London in November and £282,803 in December.

Hacan chairman John Stewart accused the airport of attempting to “buy” a new runway.

He said: “When one side can spend this amount of money to get across its view, it is not a level playing field.

“In many ways, Heathrow is buying a new runway.”

Heathrow has been contacted for a comment.