From the age of 4 to 14 children regularly eat too much salt and should reduce their intake by nearly 2g a day, the equivalent of about four bags of crisps.

Parents of four to six-year-olds are advised to be particularly vigilant because these children should not eat more than 3g of salt a day. A meal of hamburger and chips contains about 2.5g.

Another target category is boys aged 7 to 14 who must cut out at least 1g of salt a day or two packets of crisps. The recommended intake for 7 to 10-year-olds is 5g a day and for 11 to 14-year-olds 6g a day. Some of their favourite food contains high levels of salt. For example, six chicken nuggets contain 1.3g, a tin of spaghetti hoops 2g and a can of baked beans in tomato sauce just under 3g.

Babies up to six months old should eat less than 1g a day, and all the sodium necessary for an infant can be provided in breast milk. Children from 7 to 12 months should be strictly limited to 1g a day, so parents should be aware that one breadstick contains 1.07g. One to three-year-old toddlers should eat a maximum of 2g a day, though health experts believe that most would eat less, and the average for that age group now is 1.4g a day.

This is the first time that official salt limits have been issued and they update provisional limits suggested by health experts last year. The main difference today is that experts decided that four to six-year-olds should have a much lower threshold than seven-year-olds.

Sir John Krebs, chairman of the Food Standards Agency, and Sir Liam Donaldson, the chief medical officer, are also asking parents to use less salt in cooking and to avoid adding salt during meals. However, they say that the main problem is from processed food and that 75 per cent of salt consumption is hidden in this food.

Parents are urged to check labels on all food served to their children and to check how much salt or sodium is listed on packaging. A gram of sodium is equal to 2.55g of salt. There is particular concern because children’s salt intake is relatively higher than adults because they weigh less.

The Food Standards Agency has already persuaded the Food and Drink Federation, which represents the main food manufacturers, to reduce salt in a range of breakfast cereals, soups and sauces. Amounts in bread have been reduced 13 per cent since 1989.

Most companies use salt to improve the taste of products but it is also used as a preservative or for texture.

Adults are also being told to cut their daily intake to 6g, from about 9g to 12g, by the Scientific Advisory Committee on Nutrition. Typical quantities, for example, are about 1g in an adult-sized bowl of cornflakes and 4g in a large slice of pizza. Limits for babies were decided on the basis of sodium intakes from breastfeeding.

Consensus Action on Salt and Health, which has campaigned for ten years to lower salt consumption, said that a 3g reduction in salt intake in the next five years could prevent 35,000 deaths and 70,000 strokes and heart attacks.

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