Many breakfast foods commonly believed to be healthy contain a high proportion of a person's recommended daily salt intake, health campaigners claim.
Poor labelling means people could be unaware of the "hidden" salt in their breakfasts, Consensus Action on Salt and Health (CASH) said.
A study of more than 200 food items showed that, as expected, a traditional full English fry-up can contain as much as 6 g of salt – the daily limit for an adult in a single sitting.
But CASH added that those who never eat a fry-up could find that their healthier breakfast is still high in salt.
A home breakfast of coffee, orange juice, a 30 g serving of Kellogg's Cornflakes and two slices of toast with butter and Marmite contained around 2.8 g salt – nearly half the adult recommended salt limit for the day.
The saltiest "sweet" pastry surveyed was a Starbucks cinnamon swirl containing 1.74 g of salt – or the equivalent of two rashers of bacon.
Every American-style muffin surveyed by CASH had as much, or more, salt than a standard packet of crisps, while some, including Costa's raspberry and white chocolate muffin contained as much salt as three packets.
CASH nutritionist, Carrie Bolt, said: "We believe that people should be given as much information as possible about the food they buy so that they can make an informed choice."