It recently banned a Renault advert on the grounds that a large percentage of the UK's electricity came from fossil fuels, environmental advisor Don Potts told this week's ACFO conference.

In March, proposals were also put forward by Defra to tighten up the definitions of what can be counted as an environmentally friendly or sustainable product. If these come into force, they will be used as a reference point for future ASA cases.

Doubts about durability, residual value and the lifetime environmental impact of electric vehicles are limiting their appeal to fleets, according to Potts.

Speaking at the ACFO conference, he said a Europe-wide green analysis of passenger cars was needed to give consumers and fleet operators the full picture. He pointed out that opinions on durability and the carbon emissions from manufacturing batteries tended to differ and environmental claims were often vague.

He also said a clear indication of residual values was vital to the industry: 'If there's any doubt about the residual values on electric vehicles, it'll kill it stone dead. One of Britain's biggest leasing companies said to me last month they're not going to touch them until they get a definitive answer.'

The figures speak for themselves. Between the introduction of the government's £5,000 EV grant in January and the end of April only 547 vehicles have sold in the UK. London, so far, has put in only 200 of its 20,000 charging points, and points in Cambridge, Milton Keynes and Kingston on Thames haven't been used in the four months since they were installed.

Potts added: 'I'm beginning to get slightly twitchy about the future. I may have misread all this, and I'm certain someone from Renault or Nissan will say I've got this wrong, but it doesn't seem to be taking off.

'I think hybrids and electric cars have a future primarily in urban areas stop-start conditions. I don't think there's going to be any future grants for them and I think it's air quality that will drive their success and the high price for oil.'