Concerns have been raised after it was found that some pre-packed sandwiches contained as much salt as seven bags of crisps. The worrying finding came following a study by the health lobby group Consumer Action on Salt and Health (Cash). They looked at 140 sandwiches on sale and found that over 40% had 2g or more of salt, a third of an adult's recommended daily intake.

Asda's Extra Special Yorkshire Ham and Hawes Wensleydale sandwich topped the list, with nearly 4g or 65% of the recommended daily salt intake, according to the Cash survey, whilst Pret a Manger's All Day Breakfast sandwich with 3.54g of salt and the Tesco's Finest version of the same with 3.5g were second and third respectively. Cash noted that as a standard bag of Walkers Ready Salted Crisps contains 0.5g of salt, these sandwiches contain the equivalent of seven bags of crisps.

The lowest salt sandwiches in the survey were Co-op Healthy Living Tuna and Cucumber and Tesco Healthy Living Chicken Salad, with 0.6g or 10% of the recommended daily amount.

The British Sandwich Association said that it had been working hard to reduce salt levels and that the study was misleading. Jim Winship, director of the organisation, told the BBC: "Sandwiches involve the assembly of ingredients. The fact is that the salt is already in the ingredients - e.g. bacon or ham - so if consumers choose a sandwich containing these they are bound to have a higher salt content."

He stressed that on average, the sandwiches surveyed had 2g of salt, a third of the recommended daily intake, and that these levels were not unreasonable. Cash agreed to some extent with this saying that given a sandwich was often the main constituent of one of three meals in the day, containing a third of the recommended daily intake of salt was not necessarily a problem.

However, Cash said it did become a problem if such a sandwich was consumed along with a bag of crisps and some biscuits as this could could give someone their recommended daily intake of salt in just one meal.

Jo Butten, the nutritionist for Cash told the BBC that the discrepancies in salt between different manufacturers of the same sort of sandwich showed that it was possible to reduce the salt content while still being able to sell the product.

Pret a Manger, manufacturer of the second worst offending sandwich, was singled out for criticism by Cash for not detailing any nutritional information on their product's packaging. The sandwich chain rejected the criticism outright, saying it saw itself as a deli not a "factory" as the products were made on site, and that in a deli such details would not be available. It was added that customers who wanted such nutritional information could obtain from the company's website or ask one of the members of staff.

The government recommends that adults should eat no more than 6g of salt a day, although the average intake of salt is between 9g and 10g a day. Some experts estimate that if average consumption was cut to 6g a day it would prevent 70,000 heart attacks and strokes a year.