The US Embassy continues to withhold millions of pounds which could help reduce the burden on London tax and fare payers.
More than £6.1m in unpaid congestion charge penalty charge notices (PCN) is owed by the Embassy, almost £1.5m more than is owed by the Russian Embassy.
In total more than £58m is owed by Embassies and diplomatic missions in London, with debts dating back to the congestion charge’s introduction in 2003.
Although the US Embassy initially paid the charge, this policy was reversed in 2005 when officials claimed the charge was a tax from which they were exempt.
Transport for London and the Government have repeatedly denied this is the case and called on all non-paying Embassies to settle their debts.
Following his appointment in 2009, a spokesman for US Ambassador Louis Susman confirmed the Embassy would continue to withhold payment, denying the capital of funds to invest in its transport network.
Two years ago the London Assembly passed a motion calling for Mayor Boris Johnson to secure payment of all unpaid Congestion Charge fees and fines.
Johnson has repeatedly called on diplomats to “fulfil their obligations to their host city”.
Of those Embassies with an unpaid PCN, the Embassy of Peru and Australian High Commission owe the least amount with a single unpaid £60 PCN each.
The latest figures were released by Mayor Johnson in response to a question from Liberal Democrat AM Caroline Pidgeon.
In a written answer, Johnson said he was “disappointed that some Embassies continue to refuse to pay the congestion charge even though TfL and the Government’s position on this matter is clear and consistent.”