The Mayor of London is urging councils to put “politics aside” as they block Transport for London (TfL) from putting up Ultra Low Emission Zone (Ulez) signs.

Kent County Council (KCC) is one of those that is refusing to allow the relevant infrastructure for the project to be installed in the county.

It has said it will stand by its decision to not adopt any Ulez signage “for as long as there is no mitigation to minimise the impact of the expansion of the scheme on Kent residents.”

A spokesman added: “We fully understand and appreciate our obligations as a highways authority, and the safety of road users is always our priority.

“KCC is committed to the aim of improving air quality, but this must go hand-in-hand with appropriate mitigations, including better availability of public transport – something the Mayor is looking to reduce for non-Londoners with the withdrawal of the day travel card.”

The council also said plans to introduce tolls at the Blackwall Tunnel is yet another indication that City Hall has “no consideration” on how this will impact residents and businesses, as they will be “further financially penalised.”

​​The plans to extend the Ulez zone were challenged by councils at the High Court earlier this year but the case was dismissed.

This means the zone will expand from its current borders of the North and South Circular roads to encompass the outer London boroughs on August 29.

As the country prepares for the expansion, National Highways and Slough Borough Council have allowed Ulez signs to be installed on their roads but all other councils bordering the capital have not.

This includes Kent County Council, Surrey County Council and Hertfordshire County Council.

On behalf of the Mayor of London Sadiq Khan, a spokesman urged them to “put their politics aside and do what is best for their residents and drivers.”

They added: “The expansion of the Ulez was an incredibly difficult decision, but one the Mayor made to save lives and improve the health of millions of Londoners. Nine out of 10 cars seen driving in outer London on an average day are already Ulez compliant.

“Councils have a responsibility to ensure their residents and all motorists are aware of important changes that may impact drivers.

“By refusing to allow TfL to install Ulez warning signs at key junctions, these councils outside London are not fulfilling their responsibility to ensure their residents and other motorists have all the information they need to avoid driving into the Ulez inadvertently.”

City Hall said TfL has offered to pay the full cost of installing and maintaining signs.

TfL is also asking these local authorities to work with it to ensure drivers are aware they are entering the newly expanded zone.

Ulez is designed to cut air pollution in the capital by discouraging the use of high-emission vehicles - imposing a daily fee of £12.50 for those which don’t meet the criteria.