American diplomats owe London £2.3 million in outstanding congestion charge fines, it has been revealed.

The American fines constitute nearly a quarter of those owed by foreign diplomats, with the final figure hovering just below £10 million.

The Liberal Democrat’s transport secretary, Norman Baker, said the outstanding fines were “outrageous”.

“This is a perfectly proper charge and the failure to pay such a huge amount is not only extremely discourteous to the people of London and the country as a whole, but is undermining UK domestic transport policy,” he continued.

Mr Baker is tabling a parliamentary question to the Foreign Office to establish which of the countries with large outstanding charges intend to settle the bill and which have made it clear they do not intend to pay the charge.