Heathrow’s expansion could be stymied by the cost and complexity of plans to bridge the M25 motorway to build a third runway, the government is being warned by the airport’s largest operator.

British Airways owner International Airlines Group estimates bridging the M25, close to the M4 junction, would cost £2 billion-£3 billion on top of Heathrow’s already “over-inflated” £17 billion bill for the third runway.

All costs will be paid for by airlines’ customers, IAG warns in its submission to the government’s consultation on its Airports National Policy Statement, which closes tomorrow (Thursday).

IAG also claims that there is no detailed risk and cost analysis of Heathrow’s plans to build over one of Europe’s busiest motorways.

IAG chief executive Willie Walsh said: “Airlines were never consulted on the runway length and they can operate perfectly well from a slightly shorter runway that doesn’t cross the M25.”

The airport needs to focus on a shorter runway of 3,200m rather than 3,500m that does not breach the M25 and is delivered to a business case that keeps current charges the same or lower than today’s, according to IAG.

While the airline group says that Heathrow is the best option for expansion, it also welcomes credible schemes from promoters other than Heathrow.

IAG says this would ensure customers get the very best scheme, built at an affordable price, which delivers a competitive new Heathrow for the UK economy post-Brexit.

Walsh said: “Bridging the M25 means years of disruption on a motorway already plagued by delays and congestion. As well as increased costs, this will have a huge impact not only on motorists but on local communities around Heathrow.

“The airport has yet to produce a business plan that assesses the financial implications and risks of bridging the M25.
“We will not pay for a runway that threatens both costs and delays spiralling out of control and where critical elements of the project could be undeliverable.

“Britain needs cost-effective airport infrastructure that benefits the country rather than Heathrow’s shareholders.

“It is already the world’s most expensive hub airport and customer charges must not increase to pay for the new runway.

“We urge the government to benchmark Heathrow’s costs against other similar global schemes.”