Britain’s Foreign Secretary regularly reveals the amount of congestion charge debt accumulated by foreign envoys in London, and the latest report puts the figure at £116.9 million ($152 million).

The US Embassy owes the largest amount, clocking up unpaid charges and fines worth £12.4 million. The diplomatic mission accumulated a grand total of 102,255 individual fines.

This represents the total amount owed since the congestion charge was introduced in February 2003. The £11.50 ($14.96) daily charge is applied to vehicles entering the capital’s city center.

Japan came in second place, owing £8.5 million ($11 million), while Nigeria placed third, owing more than £7 million ($9.2 million).

UK Foreign Secretary Dominic Raab said the government has held meetings with the embassies, urging them to stump up the cash.

A number of embassies say they consider the congestion charges to be taxes and so, under the terms of the Vienna Convention on Diplomatic Relations, they are exempt from paying them.

However, this is disputed by the UK Foreign Office, which says there is no legal grounds to exempt diplomats from paying the charge.

"The charge is comparable to a parking fee or a toll charge, which diplomatic missions and international organisations are required to pay," a spokesman told the BBC.

"Under the Vienna Convention on Diplomatic Relations, those entitled to immunity are expected to obey the law and we therefore expect all foreign diplomats to pay their parking fines.”

Meanwhile the fines just keep totting up.