Companies which bought tens of thousands of hybrid electric cars through government grants are letting their employees run them on petrol, it was claimed.
Bosses snapped up the eco vehicles (PHEVs) through the scheme to save on paying for regular cars, The Miles Consultancy concluded after a study.
And workers who use the vehicles through a company fleet, including Audi, BMW, Mercedes and Volvo models, often don’t unwrap the charge cable, it added.
The plug-in grant, which gives buyers up to £4,500 off the new hybrid cars, was first brought out in 2011 – but was recently scrapped.
The bulk of the vehicles sold through the scheme, including more than 70 per cent of the 37,000 plug-in hybrids sold so far in 2018, were bought by company owners, figures show.
But the majority of employee drivers were not using the electric-powered capability designed to lower emissions, according to analysis by Cheshire-based firm The Miles Consultancy.
It came to its conclusion, in a study for the BBC, after examining the mileage records from 1,500 hybrid cards, with models including Audi, BMW, Mercedes and Volvo cars.
The consultancy firm, which advises 300 blue-chip companies on fuel management, found that corporate fleets averaged just 40 miles per gallon (mpg), when they could have done 130.
Figures show that in practice, however, the hybrids get 49.06 mpg, almost two thirds less than what the cars claim to offer.
The Miles Consultancy’s managing director Paul Hollick said it was “ridiculous” that workers who use the vehicles in corporate fleets were not using the electric plug-in capability.
“There are some examples where employees aren’t even charging these vehicles up,” he said.
“The charge cables are still in the boot, in a cellophane wrapper, while the company and the employee are going in and out of petrol stations, paying for all of this additional fuel.”
The British Vehicle Rental and Leasing Association (BVRLA) also hit out at the alleged practice and said companies were spurred on by the the plug-in cars because of higher taxes on diesel cars.
Toby Poston, the BVRLA’s communications director, said: “We unfortunately have got a situation where a poorly designed tax regime is driving some poor behaviours.
“We have got some situations where company drivers are choosing the vehicle based on their tax liability, rather than having the right vehicle for the right job.”
Employees often used the hybrid cars for heavy usage on motorways, he added, despite that the cars are mostly for local trips of a short distance.
A spokesperson for the Department for Transport, when presented with the findings by The Miles Consultancy, said that plug-in hybrids “bring significant environmental benefits”.
The grant for the plug-in cars has been scrapped but there will still be support for buyers, including through lower car tax rates.