An unreleased report from King’s College London shows that the proposed changes to the city’s congestion zone charges could increase CO2 emissions across the capital.

According to the report, which was prepared for Transport for London (TfL), CO2 emissions could rise 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 this will largely be caused by increased car mileage outside the congestion charging zone.

However, the authors have pointed out that the report is only a draft.

Head of research Sean Beevers said the 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”.