Labour party officials have urged the Mayor of London to put controversial plans to expand the ULEZ scheme on hold amid growing concerns it could damage the party’s electoral prospects.

The Conservatives narrowly won a by-election in Uxbridge and Ruislip – caused by the resignation of former Prime Minister Boris Johnson – with pollsters saying resistance to the introduction of the charge helped the party hang on.

Under the Ultra Low Emission Zone (ULEZ) plans, older more polluting vehicles would have to pay the charge from Greater London, potentially leading to extra costs for commuters.

Labour officials in the county have warned that party supporters have become jittery about the scheme, claiming that any widening of its scope to parts of Kent will hit already hard-pressed voters.

Shane Mochrie-Cox (Lab), deputy leader of Gravesham council, said: “If you don't have a decent transport system that is convenient for people and cost effective and the electric charging infrastructure in place so that you don't have to use your car, it is going to hurt and it Will hurt more for those who can ill-afford some of the costs of public transport.

“Where it may have been applicable in London; where they have constant tube stations, cheaper travel with buses every five minutes, when you look at the borders of the shire counties, it could be a more costly issue.”

But Cllr Mochrie-Cox said supporters were not going to back and it had the potential to cost them more when it was being headed by the London mayor, who had no jurisdiction over Kent.

The opposition Labour group on Kent County Council (KCC) recently put on record its concerns about the scheme during a full council debate on the charge.

The county authority believes the new boundaries will “disproportionately” impact on low-paid key workers who cannot afford to buy new compliant cars.

A majority of members voted in favour of a motion to ask Mr Khan to reverse the decision and will refuse to erect any ULEZ signs on KCC land.

Last year, Dartford resident criticised the mayor’s plans to expand the charge.

Angry residents and people who work in the town claimed it was a “money grab” and “unfair”.