Speaking to ITV News London, David Cameron said he had "great faith" in the Head of the Airports Commission, Sir Howard Davies. The Prime Minister added that "all options were still on the table", including an airport east of London.
Watch the interview with David Cameron in full on ITV News London at 6pm.
The accusation comes as the mayor's aviation adviser uses a speech to launch a bitter attack.
London's Mayor was said to be "profoundly unsettled" by a report which sidelined his proposal for a new airport in the Thames estuary.