Heathrow Airport is considering expanding existing terminals instead of constructing a new building as part of measures to cost expansion costs by £2.5 billion.

A number of cost-cutting design options will be put to public consultation next month amid concerns from airlines that landing charges could be increased to help pay for the work.

Heathrow claims it can complete the third runway project for a revised figure of £14 billion without compromising on passenger experience or local community commitments.

Options that would enable the cost reductions at the west London hub include installing new facilities over existing public transport infrastructure and baggage handling systems.

Other suggestions include utilising technological advancements to cut the amount of terminal space needed to process passengers and incrementally increasing terminal capacity in blocks.

Current landing charges are around £22 per passenger and a Heathrow Airport spokesman insists that the charges will remain “close to today's levels”.

Transport Secretary Chris Grayling has previously suggested that this would be a condition of giving the expansion proposals the green light.

Willie Walsh, the boss of British Airways' parent company IAG, has warned that expansion must be cheaper than the £17.6 billion budget and insisted airlines are “not going to pay for inefficient expansion”.

Heathrow's executive director of expansion Emma Gilthorpe said: "The Secretary of State set us the challenge to deliver an expanded airport for Britain with passenger charges staying close to current levels.

"We have now identified potential savings of £2.5 billion and are increasingly confident we can meet the affordability challenge.

"We are looking forward to presenting options on how to do it in our consultation in January, and while we will continue to work to reduce the cost of expansion we will not compromise on our local commitments."

Heathrow Airport is considering expanding existing terminals

The 10-week public planning consultation on the proposals opens on January 17.

A separate Department for Transport consultation on the draft Airports National Policy Statement, which sets out the Government's support for Heathrow, closes on Tuesday.

A spokesman for the government said it is on track to publish final proposals for expansion in the first half of next year for a vote in parliament.

If the scheme is approved, Heathrow will submit a planning application after consulting local communities on detailed proposals, with construction to begin in early 2021.