A report from King’s College London, which was never publicly released, shows that the proposed changes to the capital’s congestion zone charges could increase CO2 emissions across the capital, although it will reduce them within the zone.
According to the report, which was prepared for Transport for London (TfL), CO2 emissions could increase in Greater London by 182,000 tonnes.
By 2012, it says that within London but outside the zone, the increase in CO2 could be nearly 184,000 tonnes, with 2,200 tonnes saved in Central London.
It said the new charge is predicted to create a “very high disbenefit” not only for CO2 but also for NOx, NO2 and particulate emissions such as PM10.
The report indicates that the increase will be largely caused by increased car mileage outside of the congestion charging zone.
However, the authors have pointed out that the report was only a draft. Its head of research, Sean Beevers told the Daily Telegraph that its figures "need to be refined".
"This problem arose due to ambiguity in the assumptions used," he said.
Transport for London said the decision to go ahead with the CO2 charge was “based on a report which included robust research” on CO2 emissions.
“The decision was not based upon CO2 emissions estimated by King's College,” said a spokesman.
However, he confirmed that TfL is now refining its figures and “therefore the impact on air quality is likely to be significantly less than originally predicted”.
Andy Goss, managing director of Porsche, which is currently challenging the proposed new charges, said: “We always knew the environmental impact of this unfair tax would be minimal, now we know it will make matters worse.”