The rebellion against Sadiq Khan's Ulez expansion extended to the home counties on Thursday.
Councils surrounding the capital have refused to sign an agreement allowing TfL to install street signs and cameras warning drivers they are approaching the clean air zone.
It means the Mayor could be forced to create “buffer zones” on the edge of the city so drivers get sufficient notice that they face a £12.50 charge.
Buckinghamshire Council and Essex County Council have refused to give permission to install the signs, while Hertfordshire has also raised concerns about the Ulez.
It follows Surrey and Kent councils raising similar objections last week. All of the local authorities are run by Conservative administrations.
Buckinghamshire council's cabinet member for transport Steven Broadbent said on Thursday: "We support intentions to improve air quality and reduce carbon emissions, but we don’t believe this is being carried out in the right way through the Ulez expansion proposal and we have serious concerns about the impacts this expansion will have on both our residents and our roads."
He added: “We are also concerned about the potential increased number of vehicles redirecting onto our local roads to avoid entering the Ulez. Not only does this impact on traffic and road surfaces, it also has the potential to see more polluting vehicles travelling on our roads, worsening air quality for our residents."
A council spokesman said: “Alongside a number of local authorities in Greater London and the home counties, Buckinghamshire Council is refusing to sign an agreement to allow TfL to install street signs and cameras along its highways in order to enforce the expanded Ultra Low Emission Zone. “
City Hall plans to enforce the Ulez across all of London on August 29 in a bid to reduce toxic air.
It means the drivers of older, more polluting vehicles will be hit with a £12.50 daily charge.
Several of the 24 London boroughs affected have raised objections to the Ulez plan.
Harrow council’s leaders are set to issue High Court proceedings by February 24 and have cleared £400,000 to fight the expansion.
Bexley, Bromley, Harrow and Hillingdon are among those which have refused to sign agreements allowing City Hall to install cameras and signs.
However TfL can overrule the objections and install the equipment needed to police the zone using the Mayor's "direct installation powers".
But these powers do not stretch outside of the capital, with TfL is more reliant on Surrey, Buckinghamshire and Essex signing agreements for planning permission.
The home counties have asked for the £100m scrappage scheme for Londoners to be extended to their residents to give them the same “benefits and incentives for upgrading their vehicles to cleaner models”.
They also want coordination with neighbouring local authorities to “expand and improve public transport” into Greater London and a commitment that a proportion of the revenue from the extended Ulez will be reinvested to support travel options to and from the capital.
A spokesman for Mr Khan said: “The Mayor has been clear that with 4,000 Londoners a year dying prematurely from toxic air, his decision to expand the Ulez should be implemented without delay.
“In doing so we are working closely and collaboratively with the local authorities concerned to install the infrastructure needed.”
