Thousands of drivers from outside the UK are not paying London's congestion charge, the BBC has learnt.
Drivers from all over the world have left London without paying
Transport for London (TfL) is chasing more than 88,000 foreign drivers who have left owing £8.8m in unpaid bills since January last year.
So far only 25,000 of them have been identified and just £500,000 collected.
TfL said lack of a Europe-wide agreement on traffic fines meant UK local authorities had "great difficulty" tracing foreign drivers.
But a TfL spokesman said the £500,000 it had clawed back was "the highest recovery of foreign debt for traffic offences amongst local authorities in the UK".
'No legal framework'
Drivers from France were the worst offenders, leaving 25,930 unpaid bills, with Germans in second place with about 13,000.
Just 192 French drivers have so far been identified and £1,350 from a possible £2.6m has been collected.
TfL has had more success with German drivers, issuing more than 11,000 fines and recovering £261,630.
More than 10,000 Polish drivers left without paying, while Lithuania was responsible for 5,738 unpaid fines and Italians were in fifth place with 5,114.
TfL found cars from as far afield as Cambodia, Zambia and the Solomon Islands had passed through London without paying.
"This situation is not unique to congestion charging," said a TfL spokesman.
"Regretfully there is currently no legal framework in existence whereby a civil debt incurred in a foreign country can be transferred to the court system of the resident country."
But he said EU countries had recently agreed to "mutually recognise financial penalties" and that TfL would continue trying to recover the debts.
The BBC obtained the details from TfL using the Freedom of Information Act.