Research from some of the world’s leading green campaigners is pointing the finger at plug-in hybrid electric vehicles, suggesting that they emit more carbon than traditional petrol engines.

The analysis, which has been reported by the BBC, from groups such as Greenpeace has found that PHEVs emit on average 120g of CO2 per km. This figure is markedly different to the 44kg per km which is recorded in official lab tests.

According to the report from Transport and Environment, the problem comes from many PHEV owners not actually charging their cars, which means they rely solely on the petrol or diesel engine and according to Nick Molden from Emissions Analytics, that’s where the problem lies.

"If you always charge the battery and tend to do lots of short journeys, they will have very low emissions," he told the BBC.

"If you never charge the battery and drive very aggressively then they can have significantly higher emissions than the equivalent petrol or diesel model."

But with many motor industry supporters suggesting that PHEVs should be exempt from the government’s proposed ban on internal combustion engine sales, the argument is sure to rage on while PHEVs remain on sale.

“Even the report’s assumed figures show plug-in hybrid vehicles provide more than a 30% overall reduction in emissions compared to petrol or diesel,” says Mike Hawes from the Society of Motor Manufacturers and Traders.

“PHEVs also provide a flexibility few other technologies can yet match with extended range for longer, out of town journeys, and battery power in urban areas, reducing emissions and improving city air quality.

“PHEV range and performance will continue to improve meaning that, for many users, they are the essential stepping stone to a fully electric vehicle.”

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