North Circular named as London's most polluted road
The North Circular has been named London's most polluted road in a study carried out for the mayor.
The Walthamstow section of the road in north-east of the city had the worst traffic fumes, the study said.
Oxford Street ranked in the worst 15 for its estimated levels of nitrogen dioxide (NO2).
Diesel vehicles are responsible for up to 30 times more emissions than petrol vehicles, Clean Air in London said.
The campaign group's study called for diesels to be banned from London's most polluted streets by 2020.
Clean Air for London said the mayor's office released the pollution data after they had turned down three freedom of information requests and Clean Air for London used EU legislation to force the mayor's office to release it.
Of any capital city in Europe, London has the highest levels of NO2, the group said.
Clean Air in London founder Simon Birkett said: "Ultimately, the only answer is for London to eliminate completely deadly diesel exhaust from the most polluted parts of London by 2020.
"If London knuckles down and cracks the diesel problem, it could be leading the world fighting air pollution as it did 60 years ago after the great smog."
The North Circular (A406) had the highest emission rates of four out of five of the pollutants measured in the study, while the Dartford Crossing (A282) had the highest emission rate of nitrogen oxide (NOx),
Mr Birkett said it was "staggering" Oxford Street and Brompton Road - two of the busiest for shoppers, were in the top 15 worst locations in London in 2012 for emissions of NO2.
He said the levels of NO2 on these streets were 2.5 times the limits set in World Health Organisation guidelines.
He called on the mayor to follow in the footsteps of Berlin, which he said in January 2010 "made a big step towards banning all diesel vehicles" by banning pre-2008 diesel vehicles.
A Mayor of London spokeswoman said: "Strenuous efforts are being made to improve air quality in the capital and the mayor constantly reviews new measures to target the most polluted roads.
"From building Europe's largest fleet of low-emission hybrid buses to tighter emission standards for lorries and vans, the mayor will continue to work tirelessly to improve air quality in the capital."
Westminster Councillor Ed Argar said: "A long-term vision is needed to tackle congestion, but incremental change has to be the way to realise this vision - we cannot take chances with the West End economy."