OWNERS of plug-in hybrid cars should pay "considerably more" in taxes than drivers of electric-only vehicles because they are generating more than seven times as much greenhouse gas, new research has claimed.

Doug Robertson, chair of the Electric Vehicle Association Scotland, called on the UK Government to end "absurd" company car tax bandings which currently group pure electric and petrol-hybrid electric vehicles (PHEVs) in the same emissions category.

Mr Robertson, a retired mechanical engineer who oversaw the rollout of electric 'pod' cars at London Heathrow, said that workers driving a hybrid company car should pay around six times more in tax than someone using an electric-only model in order to fairly reflect their pollution rates and incentivise employers to lease the greenest possible vehicles.

Read more: Call to ban hybrid cars from electric charge points

The system - known as benefits-in-kind (BiK) - sees employees pay a percentage of the cost of their company car directly from their salary to the taxman, with employers making similarly-scaled National insurance contributions.

It currently ranges from seven per cent for electric and low-emission PHEVs to 37 per cent for the most polluting diesel vehicles.

However, Mr Robertson said bracketing electric and hybrid cars together was unfair. Instead, he has calculated alternative bandings based on the Department for Transport and US Environmental Protection Agency's "real-world" emissions figures - gathered in the wake of the VW dieselgate scandal - and recent research from Norway indicating that an average hybrid owner drives in electric mode only 40 per cent of the time.

The results estimate that while a pure electric Nissan Leaf covering 10,000 miles a year will generate 1.12 tonnes of greenhouse gases - based on someone charging the battery entirely from the National Grid - a hybrid such as a Mitsubishi Outlander will release 8.42 tonnes, more than seven and a half times as much.

He has submitted his research findings to the UK Treasury in response to a consultation on potential reforms to company car tax bands, which closed on October 20.

Read more: Glasgow City Council bans free parking for electric cars

He said: "It's quite worrying. When I did the sums I wasn't expecting the figures to turn out so badly. I was convinced that a plug-in hybrid would have been something like two or three times worse for the environment than a pure electric car, but it can only be that if it's driven 90 per cent of the time in electric mode."

Mr Robertson proposes a five per cent BiK levy for pure electric vehicles compared to 32 per cent for a plug-in hybrid. In practice, it means that if a vehicle cost £20,000 and the employee was a standard-rate taxpayer, they would pay £200 a year for an electric company car and £1,280 a year for a hybrid.

He added: "We in Britain still cling to the idea that a plug-in hybrid is a stepping stone towards pure electric uptake, but people are being misled and that really worries me. I'm not against plug-in hybrids - they are definitely better than very large diesel engine cars - but they are considerably worse than a pure electric."

Company car sales account for 60 per cent of all new registrations in the UK and the popularity of alternative-fuel vehicles (AFVs) is soaring. However, in September petrol-electric hybrids accounted for 59 per cent of all new AFVs sold, compared to a 13 per cent share for pure electrics.

Matt Walters, a senior executive at one of the UK's leading fleet management companies, LeasePlan, urged the Treasury to reintroduce a zero-tax band to distinguish pure electric cars from hybrids.

He added that the existing regime was encouraging "a shift from small, economical diesel cars to large, heavy petrol/electric plug-in hybrid cars", which could backfire.

He said: "These have the potential to greatly reduce drivers' environmental impact, but only insofar as they are driven in electric mode. If company car drivers shift to these en masse, there is a risk that average fuel economy falls and emissions increase."

A spokeswoman for the Treasury said: "The Treasury's consultation on company car tax for ultra-low emission cars has just closed. The Government will carefully consider all responses to the consultation and respond in due course."

%image('5609265', type="article-full", alt="Proposed alternative tax bandings based on "real-world" emissions")