The U.S. ambassador to Britain has refused to pay London's $14 daily toll on cars in the city center, prompting London's outspoken mayor to say on Monday he was behaving "like some chiseling little crook."

The embassy stopped paying the fee last July, shortly before Ambassador Robert Tuttle took up his post. It argues that the daily toll on those driving in central London during business hours is a tax that diplomats should not have to pay.

Mayor Ken Livingstone's office says the fee, known as the "congestion charge" and aimed at cutting traffic, is a payment for a service, not a tax.

"When British troops are putting their lives on the line for American foreign policy it would be quite nice if they paid the congestion charge," Livingstone said.

"We will find a way of getting them into court either here or in America. We are not going to have them (evade) their responsibilities."

Speaking later to the television ITV news, Livingstone, who is known for his outspokenness, said: "It would actually be quite nice if the American ambassador in Britain could pay the charge that everybody else is paying and not actually try and (evade) it like some chiseling little crook."

The embassy had decided not to pay the toll for its official vehicles on July 1, before Tuttle even arrived in Britain, and that the ambassador had not been involved in the decision, said Rick Roberts, a U.S. Embassy spokesman.

"It is a tax, it is clearly a tax, therefore ... it is not applicable to diplomats," he said. "We don't tax British diplomats (in America), we don't expect to be taxed here."

He said the embassy believed its diplomatic staff and official cars were exempt under the Vienna Convention on Consular Relations of 1963.

Germany's embassy also refuses to pay the toll, but it has not been a major problem because the embassy lies outside London's toll zone, said Michael Fluegger, a German embassy spokesman.

Roberts declined to discuss Livingstone's comments about Tuttle. "The mayor has a tendency to hyperbole," he said. "We're going to respond on the basis of fact."

Separately, Livingstone is appealing a disciplinary panel's decision that he should be suspended from office for four weeks for comparing a Jewish reporter to a Nazi camp guard.