Supposedly healthy pre-packaged sandwiches from the high street can contain "shocking" amounts of salt, saturated fat and even sugar, a report warns.

One sandwich from fast food chain Subway had the same amount of salt as nine bags of Walkers ready salted crisps, while a cheddar ploughman's from Asda had 15.2g of saturated fat - more than three-quarters of an adult woman's recommended maximum daily amount.

Research by the consumer group Which? found that many sandwiches sold by supermarkets and coffee chains have unhealthy levels of saturated fat, salt and sugar, and there is no link between quality and price. It claims consumers are often in the dark about nutritional content as sandwiches are not required to have labels carrying such information.

The nutritional analysis found that Subway's six-inch meatball marinara contains 4.7g of salt - more than 75% of an adult's 6g maximum daily intake. Marks & Spencer's wensleydale and carrot chutney sandwich was found to be high in saturated fat because of the cheese, while it also contains 25.5g of sugar - equivalent to more than five teaspoonfuls.

Which? also compared 14 chicken salad sandwiches and found the lowest priced sandwich, Morrisons deep-fill chicken salad, contained the most chicken. A chicken and rocket sandwich from Pret a Manger was found to have the highest levels of fat and saturated fat of all the products surveyed.

Martyn Hocking, editor of Which? magazine, said: "A sandwich might seem like a pretty healthy option, but there can be shocking amounts of salt, sugar and fat in some of them and you'd have no idea if they're not labelled."

A spokeswoman for Subway said it began detailing nutritional details in shops at the end of last year and is working to make its products healthier.