Boris Johnson urges Obama to make US embassy pay £3m C-charge fines

The shortfall has been mounting since the zone was introduced in 2003 after the embassy claimed it was exempt from fees.

Now Mayor Boris Johnson has said he would like President Barack Obama to rethink the policy.

Several embassies, including the US, say they are not required to pay the charge because of exemptions dating back to the Vienna Convention of 1969.

However TfL insists that it is a service charge which embassies must pay.

The call comes as Prime Minister Gordon Brown meets President Obama in Washington.

Mr Johnson said he hoped the new ambassador would reconsider the issue.

He said: "It is my hope that we will see a more co-operative approach from the United States Embassy.

"TfL continues to work with the Foreign and Commonwealth Office to persuade all embassies to meet their responsibilities and pay the congestion charge.

"More than 70 per cent of the diplomatic missions in the capital do pay the charge. TfL is actively seeking a positive resolution of this issue for all missions not currently paying the charge, including the US."

In 2006 Ken Livingstone referred to the then US ambassador Robert Tuttle as a "chiselling little crook".

Mr Tuttle has now left the post and no new appointment has been made.

However Louis Susman, one of Obama's biggest fundraisers, has been tipped for the post.

Caroline Pidgeon, Lib Dem Assembly Member who asked if the Mayor was going to ask the embassy to reconsider, said: "The amount now owed by the US Embassy to Londoners is staggering. The money, far from being insignificant, would make a real difference - for example funding miles of new cycle routes or numerous improvements to pedestrian crossings.

"A new US ambassador will shortly be appointed following the election of President Obama and I can't think of a better start to a new relationship between Londoners and the US than a change in policy from the US Embassy."

Other embassies which do not pay the charge include the Russian embassy, which owes more than £1.8million, and the Japanese embassy which in November last year owed £1.77million.

At that time foreign embassies owed TfL a total of £23million, with the US being the worst offender.

In 2006 The Embassy of the United Arab Emirates (UAE) finally agreed that its diplomats in London should pay the Congestion Charge, and has paid £99,950 for outstanding fines accrued by the Embassy from February 2003 to March 2006.