The man responsible for overseeing London's Congestion Charge has conceded that journey times in the capital are increasing - but he says the gridlock would be even worse if the scheme hadn't been introduced.
Car journey times within the charging zone have been rising since 2006, even though congestion is lower than before the charge's introduction in February 2003.
The number of vehicles entering the zone during charging hours, which are between 7am and 6pm, Monday to Friday, remains 21% below pre-charge levels.
Peter Hendy, commissioner of Transport for London, says the increasing delays are due to the building of wider pavements, bus and cycle lanes, and work to replace ageing water and gas mains.
Hendy said: 'If we had the volume of traffic within the zone that was there before the scheme started, we would be in serious trouble now.'