London, Aug 17 - A transatlantic row is brewing - over unpaid traffic penalties.

Two weeks after the installation of a new US ambassador to Britain, transport authorities in London are fuming over America's unpaid fines of nearly 3.5 million pounds, including 2.8 million pounds in congestion charges.

Murad Qureshi, a member of the London Assembly - the elected watchdog for the British capital - said Monday the Americans are the 'biggest defaulters' and are setting a 'poor example' to other diplomatic missions.

'They lead the way, and others will fall in line if the Americans pay up,' said Qureshi.

Most vehicles driving within London at peak hours have to pay congestion charges of eight pounds if paid on the day and 10 pounds if paid later.

The charge, introduced in 2003, aims to reduce traffic congestion and improve journey times by encouraging people to choose buses and trains.

Last month, Qureshi wrote to US President Barack Obama urging him to overturn the 'mean spirited' policy of not paying congestion charge implemented by the previous US ambassador Robert Tuttle.