Many new cars on UK roads emit more CO2 than older vehicles, according to new research.
Consumer group Which? claimed its tests show the latest petrol, diesel and hybrid cars are producing an average of 7% more CO2 than models released in 2017.
This is despite the UK’s pledge to become net zero for greenhouse gas emissions by 2050.
Which? looked at all 292 car models it has tested since the start of 2017 and found that typical CO2 emissions have increased from 151.6g/km to 162.1g/km.
A rise in CO2 emissions was seen across almost all car classes and fuel types.
Small petrol cars saw an average increase of 11%, while mid-size petrol SUVs rose by 20% and petrol-hybrid cars recorded a typical rise of 32%.
Which? said its findings show that cars produce more CO2 in its own tests than under official examinations.
Researchers believe for rise in carbon emissions could be due to the extra weight of modern cars, caused by an increase in size and additional technology systems.
The analysis did find that emissions linked to harming human health such as NOx (oxides of nitrogen) and CO (carbon monoxide) are a fraction of what they were in the latest models compared with those released in recent years.
Lisa Barber, editor of Which? Magazine, said: “It is shocking to see our tests uncover increasing levels of carbon dioxide emissions for the latest cars that are being built and sold to UK consumers.
“Manufacturers must ensure that they are doing everything in their power to create cleaner vehicles that are fitter for our planet and its future.”
Mike Hawes, chief executive of automotive body the Society of Motor Manufacturers and Traders, said: “We can’t comment on the results of non-official tests by commercial organisations where the methodology is unclear.
“Only the official, Europe-wide WLTP test – the toughest and most comprehensive in the world – can be relied upon by consumers to accurately compare vehicles on a like-for-like and repeatable basis.
“This shows that new cars emit, on average, some 29.3% less CO2 than models produced in 2000, the effect of which drivers can see at the pump.”