Sales of electric cars are set to fall far short of official expectations, according to a new report commissioned by the RAC Foundation which says 20 to 50 per cent of cars sold in 2030 could be hybrids.

The Committee on Climate Change has previously said it would be "feasible and desirable", to have up to 1.7 million fully electric and plug-in hybrid cars on the road by 2020.

Most industry analysts predict the number will be significantly lower. But average new car emissions in 2020 are still likely to meet the EU CO2 target of 95g/km because of the refinement of existing technologies.

Powering Ahead, a review by the consultancy Ricardo-AEA of a range of authoritative market forecasts, shows even the more positive assessments foresee only 200,000 plug-in hybrid and pure battery powered cars being sold each year in the UK by 2020.

Professor Stephen Glaister, director of the RAC Foundation, said: "Estimating future sales of electric cars is not quite like sticking the tail on the donkey, but not far from it. There are so many variables to factor in that even those paid to predict the future of low-carbon vehicles cannot agree on what is in store. The only common ground amongst the experts is that we are unlikely to see as many electric cars sold as politicians might like.

"It is more than two years since the government introduced the plug-in car grant. Yet even with subsidies of £5,000 per vehicle available only 3,600 cars have been purchased through the scheme."

Some experts think sales of these types of vehicle will actually be as low as 40,000. To put these numbers in perspective, just over 2 million new cars were sold in the UK in 2012.

In total there are around 29 million cars on the road in the UK. Powering Ahead - which was commissioned jointly by the RAC Foundation and the UK Petroleum Industry Association - analysed the predictions made in 14 other major studies for the take-up of low-carbon cars.

The report says that in the longer term, the likely mix of technologies is extremely difficult to predict. The speed with which plug-in hybrids and pure electric vehicles achieve significant market shares is highly dependent on their total cost of ownership in comparison to that of more conventional alternatives. 

This is, in turn, dependent on factors such as oil prices, further battery and fuel cell cost reductions, and government policies." 

Mr Glaister added: "This report concludes that the key to making electric cars a commercial success is a major advance in battery technology. Until then these vehicles are likely to remain too expensive and too impractical to penetrate the mass market.

"Eventually there will need to be a step change in the type of cars we drive. To help achieve this, the RAC Foundation believes a target for new car CO2 emissions of nearing 60g/km is needed for 2025. This challenging goal would help preserve the impetus car manufacturers are already demonstrating in terms of technological advancement. Electric cars might eventually come into their own: but there is no guarantee that they won''t be beaten at their own game by other low-carbon technologies."

Chris Hunt, director general of the UKPIA, said: "The key conclusions of the publication are that conventional petrol and diesel cars are expected to remain the dominant technology in the overall vehicle fleet until at least 2030 and that advances in fuel economy will be primarily achieved by continuing improvements to existing engine technology and greater focus on vehicle efficiency through reduced weight and drag.

"The study also suggests that about 60 per cent of vehicles in 2030 are likely to be powered, either in part or in full, by internal-combustion engines. Although, the factors which appear to have the strongest influence over all predictions are, firstly, future policy, and secondly, the likely speed with which breakthroughs in technology will be achieved."