Harrow Council says it has now started its legal challenge over Sadiq Khan’s decision to expand London’s ultra low emission zone (ULEZ).

The council is among three other outer London boroughs - Bexley, Bromley, and Hillingdon - along with Surrey County Council, that will fight the mayor’s plans.

In a joint statement, they have announced they launched a judicial review.

A spokesman for the mayor said it would oppose “any challenge to this vital scheme”.

The ULEZ is currently limited to the area within London’s North and South Circular roads, but is due to be extended to cover the whole of the capital from August 29.

It will then border areas of Buckinghamshire, Essex, Hertfordshire, Kent and Surrey.

Drivers of vehicles that do not meet minimum emissions standards will be charged a £12.50 daily fee for entering the zone.

The councils said they will challenge the ULEZ expansion in the High Court on the grounds that “relevant statutory requirements” were not complied with, expected compliance rates in outer London were not considered, and the proposed scrappage scheme was not consulted on.

They will also claim the overall consultation process was not properly conducted and there was a failure to carry out a cost-benefit analysis of the plan.

Harrow Council previously said it set aside £400,000 for the High Court battle.

Conservatives in London also previously claimed City Hall officials “manipulated” the final results of Transport for London’s (TfL) consultation by excluding some so-called “campaign responses”, which lowered the level of opposition in the final count from 62% to 59%.

A spokesman for the Mayor of London said: “While we’re aware of media speculation that an application for a judicial review has been made by four boroughs and Surrey County Council, neither the GLA (Greater London Authority) nor TfL have been served with their claim.

“We will be defending any challenge to this vital scheme.

“Around 4,000 Londoners die prematurely every year due to air pollution.

“The Mayor is determined to protect the lives of Londoners who are growing up with stunted lungs and more at risk of heart disease, cancer and dementia due to our toxic air.”