Pre-packed sandwiches may contain as much salt as several bags of crisps, a study suggests.
The health lobby group Cash looked at 140 sandwiches on sale and found over 40% had 2g or more of salt - or a third of an adult's recommended daily intake.
The "All Day Breakfast" variety were the worst offenders, but cheese and ham as well as chicken salad also featured.
The British Sandwich Association said it had been working hard to reduce salt levels and the study was misleading.
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 Consumer Action on Salt and Health survey.
It was followed by 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.
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 was critical of the findings.
"Sandwiches involve the assembly of ingredients," said Jim Winship, director of the organisation.
"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."
But he stressed that on average, the sandwiches surveyed had 2g of salt - or a third of the recommended daily intake - and that these levels were not unreasonable.
Cash admitted 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.
"But it's often combined with other things," says Jo Butten, the group's nutritionist.
"Once you have had a packet of crisps with your sandwich and finished off with some biscuits, you may well have gone over your limit."
Changing the bread
She said the discrepancies in salt between different manufacturers of the same sort of sandwich showed it was possible to reduce the salt content while still being able to sell the product.
For instance, Somerfield's Prawn Mayonnaise sandwich contained 43% of the daily intake of salt, while Morrison's version had 22%.
"One of the easiest way to reduce the salt content would probably be to use a different sort of bread, as that can be a significant factor," said Ms Butten.
Cash singled out Pret a Manger for particular criticism, noting that two of its sandwiches had a very high salt content but that it did not spell out nutritional details on its boxes.
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.
But all customers who were interested could ask at the tills for nutritional information, said Simon Hargraves, commercial director.
"In any event, people know that when they buy an All Day Breakfast sandwich it's not the healthiest option," he said.
"It's just not the kind of sandwich you'd eat all the time."
The British Sandwich Association also stressed that it was "it is not the sandwich industry's job to dictate to consumers what they choose to eat".
The government recommends that adults should eat no more than 6g of salt a day. However, 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.
But not all scientists sign up to those estimates, and some suggest salt does not play a significant role in those conditions.