Alex Williams, TfL’s director of customer and strategy, said: “The most recent data shows that on average, more than 96% 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 for driving in the zone, you should not ignore it.

“Your penalty will be passed to enforcement officers to recover any fines you owe, and there is a risk that your vehicle and other property may be confiscated.

“The aim of Ulez is to clean up London’s air and take old, polluting cars off the road so that no driver has to pay and no fines are imposed.

“There are only a small minority of drivers eligible for this charge, and even fewer who refuse to pay – but we would encourage anyone experiencing financial difficulties not to ignore PCNs and to engage with our staff, who will work with you for a resolution, including setting up debt repayment plans.

Mr Khan’s representatives have been contacted for comment by The Telegraph.