Passengers are paying sky-high prices for snack food on budget airlines, according to a survey today.

The average price of food and drink (excluding hot drinks) on low-fare carriers is 374% more than at supermarkets, the survey by price comparison site found.

Snacks on the no-frills airlines are also generally more expensive than those bought at airports, the survey revealed.

For example, a sandwich that costs around £2 in a supermarket and £2.40 at an airport costs as much as £4.39 on low-fare airline Ryanair and £3.95 on Flybe.

The biggest mark-ups were on items such as crisps, shortbread and muffins, while the smallest price discrepancy was on chocolate bars. A Twix bar on flights operated by bmibaby is free when you buy a hot drink.

Bob Atkinson, of, said: "Airlines can get away with charging extortionate prices because once you're onboard there's nowhere else to go. Small savings can really add up, so holidaymakers who want a few extra pounds to spend while away need to get more savvy about eating and drinking onboard.

"Prices vary significantly across airlines so by bringing your own you can avoid having to think about it at all. You can take food through security, but there's no getting around the liquids ban, so then it's worth buying any non-alcoholic drinks in the departure area and ensure that you make savings versus onboard costs as well as having far more choice available than from the airline trolley."

The survey involved checking prices at Manchester, Gatwick and Heathrow airports as well as at Asda and Airlines compared were Flybe, Thomson, Thomas Cook, Ryanair, easyJet, Monarch, bmibaby and Jet2.