By ROB HULL, MOTORING EDITOR
Environmental campaigners have warned motorists not to buy a certain type of 'green' car over concerns they produce more emissions than drivers are being led to believe.
Brussels-based think tank Transport & Environment said these electrified cars are not only more polluting than manufacturers claim, they're also a lot pricier to run than a fully-fledged EV.
Dubbing them a 'smoke screen', the group said plug-in hybrid electric vehicles (PHEV) are a 'growing emissions scandal' and 'the biggest con in automotive history' - a bold statement given the recent car finance impropriety and this week's High Court 'dieselgate' trial with 1.6million UK drivers taking legal action against car makers over accusations of cheating diesel emissions tests.
The report comes in the wake of September plug-in hybrid registrations growing by 56 per cent year-on-year.
PHEVs are widely considered the ideal stepping stone between a traditional combustion engine car and EVs.
This is because they have a petrol engine that's supplemented by electric motors, which are powered by a small onboard battery. They're most efficient when fully charged using a public device or domestic wallbox.
They too offer lower benefit in kind taxation due to their low 'official' CO2 emissions, making them incredibly appealing to company car drivers.
But T&E says real-world measurements show they emit five times more carbon dioxide than claimed.
Dubbing them a 'smoke screen', Transport & Environment said plug-in hybrid electric vehicles are a 'growing emissions scandal' and 'the biggest con in automotive history'
Its study, based on 'new evidence' collected from 127,000 vehicles, also claims that PHEVs cost the average driver over £650 more a year to run than motorists think based on their official fuel economy figures, making them 'less cost effective than a fully electric car'.
Tim Dexter, T&E UK's vehicle policy manager, said: 'Plug-in hybrids look green on paper, but the reality is they pollute far more and cost hundreds of pounds extra each year to run.
'It’s unacceptable that outdated official tests continue to mislead consumers - drivers deserve to know what they’re really buying.'
Some 172,639 new PHEVs have entered Britain's roads this year.
While this is more than diesel sales (83,656), it's 50,000 fewer than conventional 'self-charging' hybrids - those that don't need to be plugged in but have smaller batteries and therefore shorter electric-only ranges.
One hundred per cent electric vehicles are also outselling PHEVs by almost two to one with 349,414 registrations between January and September 2025.
Petrol cars are more than four times as popular as plug-in hybrids this year.
However, T&E has taken umbrage with the 56 per cent surge in sales last month, with 38,308 PHEVs snapped up in September.
combustion engine car and EVs. This is because they have a petrol engine that's supplemented by electric motors, which are powered by a small onboard battery. Pictured: the internal workings of the Range Rover PHEV drivetrain
The report suggest that PHEVs emit just 19 per cent less CO2 per kilometre, on average, than petrol and diesel cars, which the think tank says is a 'stark contrast' to industry claims.
When tested on the road, the study found that emissions are almost five times higher than official figures.
T&E admits this is partly due to owners infrequently charging them and instead relying on the petrol engine for most of the journey.
And the gap between industry claims and real-world emissions is said to be getting worse.
When the think tank carried out the study in 2021, it found that PHEVs were typically producing 3.5 times their claimed CO2 emissions.
'Poor design, low charging rates, and frequent reliance on the combustion engine mean drivers gain little financial benefit,' the report said.
'On average, UK drivers spend over £800 more a year on fuel and charging than advertised as hidden fuel use drives up costs.'
T&E also said motorists are being overcharged for PHEVs on false promises of their green credentials.
In 2025, the average PHEV in the UK, France and Germany cost £48,500 - a full £13,000 more than a battery electric vehicle, it estimated.
Volvo in August released its latest PHEV model, the XC70 (pictured). Available first in China, it offers a giant 124-mile range, which is on par with the range of some EVs on sale today, like the Mazda MX-30
T&E said choosing a medium range PHEV, like the VW Tiguan (left), over a comparable EV, such as the Kia EV3 (right), would leave drivers £1,500 worse off every year
'Put simply, choosing a medium range PHEV, like the VW Tiguan, over a BEV, such as the Kia EV3, leaves drivers about £1,500 worse off every year.
'Yet despite higher purchase prices and running costs, carmakers still push PHEVs as the sensible choice,' the study concluded.
Dexter added: 'Plug -in hybrids are one of the biggest cons in automotive history costing drivers far more than they realise.
'The real smart, affordable choice is to go all in on electric.'
Colin Walker, head of transport at the UK's Energy and Climate Intelligence Unit (ECIU) think tank, said the Government's recent decision to allow new PHEVs (and conventional hybrid cars) to remain in showrooms until 2035 - five years after conventional petrol and diesel models are outlawed - could have environmental ramifications that 'echo the infamous Dieselgate scandal'.
His comments come a decade after Volkswagen's emissions cheating 'defeat devices' were exposed - and in the same week a pivotal trial at London's High Court began, with 1.6 million motorists taking legal action against major car makers accused of eluding CO2 tests.
The claim is the largest of its kind in English history, with the High Court previously told it is believed to be worth at least £6billion.
Tim Dexter, T&E UK's vehicle policy manager, described plug-in hybrids - like the Alfa Romeo Tonale PHEV pictured - as 'one of the biggest cons in automotive history costing drivers far more than they realise'
Walker went on: 'The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark.
'Consumers are being duped into believing that, in buying a PHEV, they are helping the environment and saving money.
'In reality, PHEVs are little better than regular petrol and diesel cars when it comes to the fuel they consume, the CO2 they produce and the money they cost to run.'
He added: 'Rather than distracting people with this outdated and expensive technology, the Government and car manufacturers could instead focus on helping regular families make the move to EVs - which, besides offering genuine reductions in greenhouse gas emissions, are capable of saving their owners hundreds, even thousands, of pounds a year in running costs.'
Mike Hawes, chief executive at the Society of Motor Manufacturers and Traders, said: 'Manufacturers have invested billions to help record numbers of drivers go electric, and most would never go back once they do.
'However, some drivers are understandably anxious, especially those with concerns over charging availability.
'For them, plug-in hybrids, which, when used as designed, can combine the best of both worlds - offering reassurance about the charging experience while cutting emissions, thus providing a crucial stepping stone towards a full EV.'