TfL announced that more than 1,400 vehicles had been taken from their owners in the past year, generating more than £700,000 to pay off fines.

TfL said: “If the registered keeper of a vehicle fails to pay the penalty, it is recorded as an unpaid debt and an order is made for its recovery. If the amount is still not paid, this gives rise to a court-issued arrest warrant and enforcement action to recover the unpaid debt.

“If a registered keeper ignores a warrant, bailiffs will attend their address to collect the money owed.”

Pressure is mounting on London Mayor Sadiq Khan to get to grips with the problem.

Mr Khan championed the ULEZ project and encouraged its expansion into outer London boroughs last summer.

But the news forced the London Assembly to write a letter to the mayor demanding action be taken to recover the fines.

Neil Garratt AM, chairman of the Budget and Performance Committee, warned that transport projects would face a blockade if revenues could not be located.

He said: “The ultra-low emissions zone appears to have contributed to an almost £300 million increase in bad debts in three years, a pressing financial problem for TfL.

“Such large sums of money owed to TfL, which may not be recoverable, mean much-needed transport investment projects could be abandoned.

“That is why we have today asked the Mayor to consider appropriate measures to increase the collection levels of road pricing schemes, and also to provide details on the bad debt ratio before and after the expansion of ‘ULEZ on the outskirts of London in 2023.

Earlier this year, Neil challenged Mr Khan, asking if motorists would see “bailiffs knocking on people’s doors?” »

Mr Khan reiterated that “all options” were open and stressed the importance of securing the funds.

Speaking over the summer, the Mayor added: “TfL has been working to identify new ways of recovering debts, including engaging with the Department for Transport and the DVLA and working with enforcement officers enforcement to find drivers who receive multiple PCNs and improve communications with drivers. »