For the first time, the agency has published targets for salt levels in children's food during cooking, at the table and in shop-bought meals.

The findings raise concerns that children could develop health problems later in life from high salt intake linked to increased blood pressure.

The FSA suggests babies under six months old should have less than 1 gram of salt a day and those aged seven to 12 months one gram a day.

Children aged one to three should have 2 grams of salt a day; children aged four to six, 3 grams a day; those aged seven to 10, 5 grams a day; and children 11 to 14, 6 grams a day.

Professor Sir Liam Donaldson, chief medical officer for England, said reducing salt intake would improve the nation's health.

"A multi-pronged action is required to reduce the population risk of developing high blood pressure, which includes cutting the level of salt in the diet along with encouraging children and adults to eat more fruit and vegetables, maintain a healthy weight and be physically active," he said .

Official studies on salt intake in children show most consume above the targets, but the FSA said the results were an under-estimate because they excluded salt added during cooking and at the table.

Sir John Krebs, chairman of the FSA, said: "While consumers can add less salt at the table and in cooking, they cannot change the amounts of salt in processed foods, which make up, by far, the highest proportion of our salt intake.

"This is the responsibility of the food industry."

Industry action

The Food and Drink Federation, which represents manufacturers, said salt levels in many processed foods had fallen substantially in recent years.

It said salt in breakfast cereals had dropped by 16% over the past three years, while soups and sauces were expected to lose 10% this year.

Its director general Sylvia Jay said: "UK food and drink manufacturers are committed to encouraging consumers of all ages to improve their own health through a balanced diet.

"Whilst there is currently a medical debate about the effects of sodium on health, the Food Standards Agency (FSA) has advised consumers to reduce salt intake. Our industry is glad to cooperate with the FSA to help achieve that end."

Kraft Foods, which makes the popular children's Dairylea Lunchables snack, has announced it is cutting the average salt content from 2.5 grams to 2 grams a pack.

"The whole thing about Lunchables is that they should be bought as an occasional treat and our research shows that many youngsters don't have more than seven or eight a year," said Bob Fenton from Kraft Foods.

Fastfood chain McDonald's was also due to announce salt reduction targets soon.

A McDonald's Big Mac contains almost 2.3 grams of salt and a portion of large fries just over 1 gram.

"Historically we have reduced salt levels in a number of areas such as sauces and we will be looking at the new guidelines in the context of our current and future menu," a spokesman said.

The campaign group Consensus Action on Salt and Health welcomed the FSA guidelines, saying they were long overdue.

Labour MP Kerry Pollard, who has worked with the group, urged manufacturers to reduce salt levels in food.

"Manufacturers and retailers must take more responsibility for the nation's diet and should work together to offer healthier foods with less salt to their customers."