Pret’s cheddar and pickle baguette, £4.50 on the high street, was 37 per cent more expensive at Stansted, where it goes for £6.20.
A study published this week by the Office of Rail and Road (ORR) estimates that the average food retailer is charging a premium of around 10 per cent for food and drink in stations.
The watchdog used mystery shoppers to visit some of the most popular station outlets and compare them with high street prices.
They found that retail prices at airports for common purchases like bottled water and cola are up to 12 per cent higher than at rail stations.
The ORR said the evidence also suggests that customers were less satisfied with station catering, with 9 out of 10 brands holding a lower average review at stations.
Station operators told the ORR that they prefer to take a “hands-off” approach to retail prices and carry out little in the way of formal monitoring and do not try to influence prices.
Pret A Manger, Leon and WH Smith have been approached for comment.