Travellers heading into and out of Heathrow have been warned they may face a new charge when the ULEZ (Ultra Low Emission Zone) is extended – with a potential £25 fee for using Britain’s busiest airport.

The scheme that charges certain vehicles to drive into and out of the capital currently covers an area of inner London inside the north and south circular roads, but in a bid to boost air quality, London Mayor Sadiq Khan is expanding the ULEZ to the whole of the capital. Drivers will be billed a £12.50 surcharge from August 29 this year to drive into areas of London including Heathrow, unless their vehicles meet the emissions requirement, with the same charge if exiting on a different day.

The changes mean those who choose to leave cars that don’t meet the emissions requirement at or near the airport will be charged an additional £25 on top of any parking fee, with the AA (Automobile Association) issuing the warning to those unaware of the full effect of ULEZ.

“Many holidaymakers will consider the ULEZ expansion as a London issue, but the reality is that the new boundaries take in much more than people anticipate,” said Jack Cousens, head of road policy at the AA.

“Drivers and taxi firms from outside London will be hit with a hidden charge so Heathrow, TfL (Transport for London) and travel agents need to tell holidaymakers about the charge.”

Whitehall officials are looking into the possibility of central Government blocking the Mayor’s ULEZ extension, with five councils ready to take legal action to challenge the plans: Bexley, Bromley, Harrow, Hillingdon and Surrey.

The ULEZ enforcement is based on declared vehicle emissions rather than a car’s age, with estimates putting a figure of four out of five cars already meeting the standard required.

Petrol cars that effectively pass the ULEZ test are mostly those first registered after 2005, although cars that meet the standards have been available since 2001. Diesel cars that meet the standards are generally those first registered after September 2015.