Mr Clarke said: 'This is a deliberately misleading distraction away from the reality that their own customers have to pay pump prices, while users of other fuel cards enjoy major discounts which deliver significant cost savings.

Commenting on the suggestion that drivers have to deviate from their routes to refuel if using branded fuel cards, he added: 'Remember, these so-called "restricted" fuel cards are for such networks as BP, Esso, Shell, Texaco and so on. Even a driver who forgets to refuel until their warning light comes on still has several miles' worth of fuel in the tank. What kind of route could they possibly be on that would not soon take them past their chosen brand of service station?'

Mr Clarke branded the 'route deviation' argument as a 'complete red herring' and said: 'A driver carrying a Shell fuel card, for example, has access to more than 1,100 sites nationwide. There are in excess of 1,200 facilities in BP's national network. If the driver is "restricted" to Texaco, they can refuel at over 1,700 service stations across the country and so on.'

Finally Mr Clarke explained why he believes the claims have been made and said that fleets using a fuel card with a typical discount could expect to achieve significant annual savings.

To fleet managers, he commented: 'Use some common sense. A fuel card supplier which can not – or will not – offer discounts has got to find something to attack its competitors who can offer its customers massive savings. Route deviation? It is nonsense and, although you can not blame them for trying, Arval knows very well that it is nonsense.'