Families are buying fuel cheaply before they set off for holidays rather than paying more at motorway filling stations, a new survey has found.

The study of more than 1000 drivers found that almost all said the cost of filling up their cars or camper vans with petrol or diesel at motorway stops was too much. More than half of those questioned admitted they always bought their fuel more cheaply before setting off on their journeys.

The poll, by Viewsbank, comes as thousands of ­families set off over the weekend at the start of the Scottish school summer holidays to stay with friends, relatives or to travel to other destinations across the UK and Europe.

The poll also showed that 28 per cent of drivers always fill up before going on a motorway.

It found that 5 per cent of those questioned always leave the motorway to find cheaper fuel elsewhere rather than fill up at service stations.

A further 27 per cent will only fill up on the motorway if they are almost out of fuel, with 84 per cent saying the high price of petrol and diesel puts them off buying anything else from motorway service stations.

However, the poll also revealed that 35 per cent of motorists use motorway service stations at least once a month. Just over 10 per cent using them at least once a week.

Drivers are most likely to use service stations for going to the toilet and stretching their legs.

More than 30 per cent who stop eat their own food but 24 per cent do eat at restaurants. Although drivers are recommended to take breaks every two or three hours, 32 per cent of those polled will drive for more than that, while 9 per cent will drive for four hours or more before stopping.

David Black of Viewsbank said: "Motorway service stations definitely provide an important service and millions of motorists use them. But the research shows they are not winning many friends.

"Customers are convinced they are paying too much and only use them because they don't have a choice."

Not only fuel makes motorway driving expensive, surveys find food and snacks at service stations are more expensive that those in the high street or supermarkets.