The clean air zone currently applies to local bus services only, but council documents shared with the Local Democracy Reporting Service show that expanding it “to cover commercial vehicles and, if appropriate, private cars” is being considered.

The Liberal Democrat opposition group has framed this as “a secret plan to introduce ULEZ” but Labour has said this is “scaremongering.”

The clean air zone requires buses to meet Euro VI emission standards as a minimum, or be fully electric.

Executive member for environment and climate emergency, Coun Kate Ravilious, said: “This idea, suggested by council officers, is one of many to stimulate discussion around what measures councillors want to consider to improve air quality in York, and is therefore not administration policy.

“Liberal Democrats are once again scraping the barrel by making claims they know to be untrue and in doing so, have opted to follow Sunak’s scaremongering tactics rather than be factual with the York public.

“This administration is committed to clean air and affordable ways to get around and this is the start of a conversation with the York public, and councillors, about how that is achieved”.

Liberal Democrat group leader Coun Nigel Ayre said: “We asked for clarity from the Labour administration at the executive meeting on Thursday on their plans for the clean air zone.

“These discussions should not be held in secret.

“We have seen in all the public papers that the clean air zone is likely to just cover freight and taxis with no suggestion that private vehicles would have to comply.

“However, in an email sent to all councillors asking for comment on Labour’s policy ideas for the upcoming transport plan was the suggestion that private vehicles come under an extension of the clean air zone.”

Coun Andrew Hollyer said: “Residents deserve an explanation from Labour about their secret ULEZ plans.”

He added: “We want to see action on air pollution, which is why the council needs to focus on the policy ideas that will see a reduction in the need for car journeys and will make a sizeable impact on the climate crisis.”

Coun Chris Steward, Conservative group leader, criticised the Liberal Democrats over their comments.

“This does seem that the Lib Dems are looking for column inches rather than anything tangible and is the very sort of headline-grabbing silliness that York residents are sick of,” he said.

“Labour is doing a consultation on transport and it is understandable that this will therefore feature a number of options.

“The Conservatives have been clear that we would oppose any sort of congestion charge and indeed submitted a full council motion ruling it out, with this being passed in July.”

Other policies that have been suggested to improve air quality in York are to expand electric vehicle charging facilities to keep pace with public demand, as well as to support the development of green infrastructure along transport corridors.

Council officers are also considering replicating Oxfordshire County Council’s ‘carbon reduction hierarchy.’

This includes prioritising actions that avoid energy consumption, such as avoiding unnecessary journeys, and actions that save energy, such as replacing street lighting with LEDs.

Clean Air Zone York: Council considers extending clean air zone in York to cover private cars