As Mayor, Mr Johnson introduced the original ULEZ scheme for central London but accused Mr Khan of dreaming up a “mad lefty policy” to pay for his mismanagement of Transport for London (TFL).
The intervention also suggests Mr Johnson may still be thinking of fighting his west London seat of Uxbridge and South Ruislip rather than heading to rural Oxfordshire for a safer constituency at the next general election.
In a video message posted on social media, the former Prime Minister insisted that for air quality purposes the expansion of ULEZ was “completely unnecessary.”
He said: “I know quite a lot about improving air quality in London. I brought in a lot more cycling, I brought in new hybrid buses, I brought in green electric taxis and we got nitrous oxide down by 20 percent.
“We got [particulate matter polution] down by 15 percent and that was even before we brought in the ULEZ for inner London.
“You don’t need an all London emissions zone. It’s inner London that has the air quality problem.”
He went on: “You don’t need an outer London emission zone in the way Sadiq Khan is imposing one because by 2030 all new cars in this country are going to be much cleaner and greener anyway.
“There’s only one reason why he’s doing it and that is because he has bankrupted TfL by his mismanagement of the finances of London and he wants to rake in money from motorists in outer London and beyond in a way that is completely unreasonable and unnecessary for air quality.”
He added: “So stop Khan’s mad ULEZ expansion plan. Fight his plans to take money off hard pressed motorists at a very difficult time and stop this mad lefty tax on people’s lives and livelihoods.”
The blistering attack comes as four London borough councils are taking Mr Khan to court over his plans after he ignored a clear majority against the proposals in the public consultation.
Other councils in London and outside have refused to put up the cameras and infrastructure necessary for ULEZ to work.
It was also claimed that Khan personally intervened to remove 5,000 representations against his plans from members of the Fair Fuel Campaign.
READ MORE: Sadiq Khan under huge pressure as ‘penny dropping’ over hated Ulez
Mr Khan though has been unapologetic about the policy, recently telling a Commons committee that it showed he is a “strong leader” arguing that there is a difference between a consultation and a referendum.
He has insisted that it will save thousands of lives every year but a Tory council leader has accused him of using ‘nonsense data’ to back his claims.
The £12.50 ULEZ charge is for vehicles that do not meet up-to-date emissions standards, which currently covers inner London and applies to petrol cars older than 2005 models and diesel older than 2015.
This is in addition to the £15 daily congestion charge for all vehicles in the very center of London.
The ULEZ expansion – introduced by Mr Khan – will cover all of London, from the center down to Chessington and up to the M25.
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