Alex Williams, TfL’s chief customer and strategy officer, said: “The most recent data shows that on average, over 96 per cent of vehicles seen driving in the Ulez are compliant.
“We want to send a clear message to vehicle owners that if you receive a penalty charge for driving in the zone, you should not ignore it.
“Your penalty will progress to enforcement agents to recover the fines that you owe, and there is a risk that your vehicle and other items of property will be removed.
“The aim of the Ulez is to clean up London’s air and remove old polluting cars from the road so no drivers need to pay and no fines occur.
“There is only a small minority of drivers who are eligible for the charge, and even fewer who are refusing to pay – but we encourage anyone experiencing financial difficulties not to ignore PCNs, and to engage with our staff, who will work with you towards a resolution, including setting up debt payment plans.”
Mr Khan’s representatives have been contacted for comment by The Telegraph.