Newest cars pump out more CO2 than predecessors - including 'green' hybrid models

Many of the latest cars are pumping out more carbon dioxide (CO2) than their predecessors - because they are bigger, heavier and carrying more technology.

Some of the worst offenders are producing almost a third more CO2 than older models, representing a big challenge as the government aims for net-zero carbon emissions by 2050.

Consumer group Which? analysed the results from every model it had tested since the start of 2017.

Each car was examined under "lab-controlled conditions", given 200kg of luggage and tested with the radio and air conditioning on to replicate everyday use.

Which? found that the 292 petrol, diesel and hybrid vehicles were producing 7% more CO2, on average, then their predecessors.

The increase was "seen across almost all car classes and fuel types", it said.

There were big differences between categories, however.

Large petrol-hybrid models - which many buyers may view as a green choice because they supplement the traditional engine with an electric motor - showed a rise in CO2 of 31.7%.

Mid-size petrol SUVs were found to be emitting 20.4% more CO2 than their predecessors.

The figure for small petrol cars rose by 11.2%, while the rise for mid-size diesel SUVs was 6.4%.

There was an average increase in CO2 of 10.5g/km - going up from 151.6g/km to 162.1g/km.

The added size and weight of modern cars is one of the main reasons, Which? said.

While carmakers had "invested in lightweight materials", the ballooning of the latest models had contributed to an "overall weight gain".

On a more positive note, NOx (oxides of nitrogen) and CO (carbon monoxide) emissions, which are harmful to human health, are now a "fraction of what they were compared to cars made in recent years", the group said.

In petrol cars, it found the level of CO had dropped by 40.6% on average.

For diesels, the decease in NOx was an average of 84%.

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."