Congestion charge has had no effect on reducing London's pollution, finds study
Researchers found that the introduction of the controversial charging zone in Central London made no difference to the levels of smog and noxious gases.
In fact, some pollutants actually rose when the charge came in because of the extra buses and taxis on the roads.
The new findings come as dozens of councils are considering bringing in road-pricing schemes to improve the flow of traffic and boost city air quality.
Professor Frank Kelly, an environmental health expert at King's College London, said congestion charges that covered only small parts of cities did little to cut air pollution.
"The problem was that the central zone was only 1 per cent of the Greater London area," he said. "Even though it reduced the traffic by 40,000 vehicles a day, there was a dramatic increase in the number of buses.
"So the benefit was to some extent offset by the rise in public transport."
The capital introduced the charge in 2003, when drivers had to pay £5 to enter an eight square mile area of the city centre. Since then the toll has increased to 8 and the zone extended.
The scheme, which was introduced to cut traffic rather than pollution, initially had a dramatic impact. By 2006, the number of motorists driving through the capital's streets had fallen by a fifth.
However, Professor Kelly's team, who took air samples two years before and after the charge was introduced, noticed little change in pollutants such as smog, diesel soot and carbon monoxide.
The professor believes that expanding the zone to all of London would have "a small but important impact on air quality".