Transport for London (TfL) has hit back after the US ambassador said his staff would not pay the London congestion charge on principle.
The charge is a tax, maintains the US
US ambassador Robert Tuttle told the AM programme on BBC One it was a municipal tax which meant diplomats were exempt.
TfL said: "It is the British government and the British courts, not the US ambassador, which decide what is a charge and what is a tax."
US embassy staff have racked up a bill of £270,000 in unpaid congestion fines.
Mr Tuttle maintained the £8 congestion charge was a tax and said State Department lawyers agreed with him.
The US ambassador is claiming diplomatic immunity under the 1961 Vienna Convention, which gives protection against paying taxes, and has said several embassies do not pay.
The TfL spokesperson said: "The Foreign Secretary told MPs in November they had informed missions of their view that the congestion charge did not constitute a form of direct tax but was a charge analagous to a motorway toll and they were expected to pay.
"It is worth noting that the US Embassy does pay similar tolls in both Oslo and Singapore and indeed they also paid in London until the new Ambassador arrived."
London' s Mayor Ken Livingstone is already in hot water for allegedly likening the Ambassador "a chiselling little crook".