Costs of expanding Heathrow and the timetable for delivery must be clarified as a matter of urgency, according to the aviation regulator.

Civil Aviation Authority chief executive Richard Moriarty says in a letter to the Department for Transport that he is concerned about Heathrow Airport’s ability to provide “high quality information” about the costs of the scheme associated with the current stage of the masterplanning process.

It also calls on the airport to provide assurance that a revised timetable to launch a statutory consultation will allow time for “effective engagement with the airline community”.

Airlines have expressed concern to the regular over the last 18 months about the lack of comprehensive detail from Heathrow on the costs and efficiency of expanding the airport, it added.

However the CAA also said that it fully appreciates that Heathrow is still developing its preferred masterplan “so some uncertainty is inevitable given the maturity of the design”.

International Airlines Group, which owns British Airways, said: “Heathrow is the most expensive hub airport in the world. It’s outrageous that it has yet to provide a detailed breakdown of the £14Bn expansion costs.

“The CAA is right to demand this as the regulator needs to ensure that passenger charges don’t rise from current levels and the UK benefits from cost effective infrastructure so that it can compete on a global scale post Brexit.”

A Heathrow Airport spokesman said: “We continue to engage with all of our stakeholders on our expansion plans and look forward to presenting a detailed preferred masterplan for further public consultation next year. We remain on track to submit a planning application in 2020 and for the new runway to open in 2026.”

Photograph: Heathrow Airports Limited