The firm reckons that electricity should cost "about the same as petrol", which would reduce the incentive for fleets and individuals to change to an electric car – however it says that massive investment is needed to generate new plants as well as upgrades to the ageing national grid if the Climate Change Committee's call for 1.7 million electric cars on Britain's roads by 2020 is to become a reality.

The firm has estimated that such taxes would raise £1.7 billion a year, which, if kept exclusively for the purpose, could pay for one new nuclear plant, two gas-fired power stations or 10,000 new wind turbines each year.

Saturn Energy managing director John McShane said: 'Even with the grants these cars won't be cheap.

'The running costs of an electric car, if you can afford one, look attractive – two pence per mile compared with, say, 12p for a conventional car.

'But putting a million on the road will mean having to build new power stations to keep them charged when we're already concerned about power shortages.

'If the electricity used to charge these cars cost about the same as petrol then that may provide the investment we need.

'Nervousness in the economy is killing investment in new and renewable energy and the Government really is the only one that can spark the required investment to change this position.'