Heathrow Airport bosses will be "doing themselves a great disservice" if they fail to meet their commitments on landing charges to pay for a new runway, the head of the aviation regulator has warned.
Richard Moriarty, who became chief executive of the Civil Aviation Authority (CAA) last month, declared his organisation will "put a lot of pressure on Heathrow to rise to the occasion".
On Monday night the Government easily won a Commons vote in support of the third runway, which Heathrow says will be privately financed at a cost of £14 billion.
In an interview the following morning, Heathrow chief executive John Holland-Kaye refused to strengthen the airport's previous commitment of keeping landing charges "close to today's levels".
It would be "foolish to guarantee flat charges at this stage", he told the Today programme on BBC Radio 4.
Speaking to a gathering of travel and airline leaders in Westminster, Mr Moriarty said: "Be very clear, we will be using our voice to make it abundantly clear to Heathrow that all that they've said about keeping airport charges affordable in the past will continue now that the vote in Parliament has been successfully given.
"If you look at all of our communications with them, we repeat this back regularly. I was with Heathrow only last week making this point to them.
"I think Heathrow would be doing themselves a great disservice if a week following the vote, they suddenly walk back from what has been, in all fairness to them, a commitment to work towards affordable charges that they have given over the past few months and years."
Mr Moriarty told the summit hosted by trade organisation Abta that the uncertainty over the project is "an uncomfortable position to be in", but stressed it is "still early days".
Following Monday's vote, Willie Walsh, chief executive of British Airways parent company IAG, said he has "zero confidence" in Heathrow's ability to keep charges flat.
"It's only a matter of time before we start hearing excuses for massive cost escalation," he predicted.