Children's sweet treats are as salty as many savoury snacks, according to health campaigners.
Some of the most popular biscuits contain more salt than popcorn, chicken nuggets or fish fingers.
Now parents have been warned that feeding too many to their children could increase their risk of high blood pressure or even a heart attack in later life.
In the research by Consensus Action on Salt and Health (CASH), more than 110 biscuits were as salty as, or saltier than Butterkist salted popcorn.
They placed the treats among the top ten contributors to salt intake in the British diet.
Asda's fun size mini milk chocolate digestives were the worst offender, with 0.4g of salt per 25g bag.
Sainsbury's giant white chocolate and raspberry cookies packed 0.39g per 60g biscuit.
McVitie's mini gingerbread men had 0.3g of salt for every 25g pack while its dark chocolate hobnobs delivered 0.2g per 19g biscuit.
For comparison, a Birds Eye fish finger contains 0.2g of salt per 28g finger. A Sainsbury's chicken nugget has 0.24g of salt per nugget.
The adult recommended daily allowance is 6g, but for under-threes it is just 2g.
Sonia Pombo, a nutritionist for CASH, said: "A lot of people realise that biscuits have a lot of sugar in them but we are trying to point out there are other health issues too."
According to the campaigners, 80 per cent of under-tens eat one or two biscuits every day.
The survey found big variations in salt in various brands, often of the same biscuit type. McVitie's milk chocolate digestives had 0.2g per biscuit, against 0.09g in a digestive sold under the Sainsbury's So Organic label.
Cash called on stores and manufacturers to cut salt content and introduce clearer labelling. Some labels show sodium rather than salt content. 1g of sodium is about 2.5g of salt.
Some traditional favourites, including custard creams and bourbons contained only 'trace' levels of salt.
But experts were surprised by the other findings.
Graham MacGregor, professor of cardiovascular medicine at Queen Mary, University of London said: "With salt hidden in sweet foods as well, how can parents be expected to prevent their children from eating too much, putting them at risk of high blood pressure as adults?"
Asda has promised to relaunch its fun size digestives in six weeks after a 'reformulation' to halve the salt content.
Sainsbury's insisted it had been working to reduce salt in own brand products for 13 years.
A spokesman added: "We think it's wrong to include giant cookies as they weigh a considerable amount more than the other biscuits featured. They are clearly meant as an indulgent treat, not an everyday snack."
Suggested For You
Get top stories and blog posts emailed to me each day. Newsletters may offer personalized content or advertisements. Learn more