Britain’s motorway services are among the most expensive places to shop in the UK, according to research by What Car?.

What Car? discovered a WH Smith motorway services outlet that was charging consumers a 91% motorway mark-up over its high street outlets on a 750 ml bottle of water – more than Harvey Nichols in Knightsbridge.

M&S also charges inflated prices in its motorway shops, including a 25% increase on a bottle of water, 16% on a sandwich and 15% on a large sausage roll. Even fast food outlet Burger King charges 12% more on the motorway than it does in its high street restaurants.

Fuel is more expensive, too, with motorists having to pay an average motorway levy of 5.2% for unleaded fuel and 3.4% for diesel. Consumers filling their fuel tank at motorway services will pay on average £77.00 more per year than they would if they filled up off the motorway.

What Car? editor-in-chief Steve Fowler said: “It is unforgiveable for retailers to take advantage of motorists in such a brazen manner. With fuel prices at an all-time high, the 5.2% average motorway fuel mark-up is hard for consumers to fund, and a 91% mark-up on a bottle of water is utterly unacceptable. We suggest that all motorway users plan their journeys carefully and try to avoid using such greedy retailers as much as possible.”

The research was carried out after a What Car? poll revealed that two thirds of consumers feel they get ripped-off every time they visit a service station.