It is almost four times as salty as breast milk, say researchers who have found that those fed cow's milk before 12 months tended to have the highest salt diets.

Dr Pauline Emmett and Vicky Cribb, nutritionists from Bristol University, found that seven in 10 babies had too much salt in their diets.

The study, published in the European Journal of Clinical Nutrition, looked at almost 1,200 eight-month-olds born in 1991 or 1992.

Cow's milk, they noted, contains 55mg of salt per 100ml, almost four times that found in breast milk (15mg / 100ml). Concentrations in formula milk vary from 15 to 30mg / 100ml.

A baby consuming 700ml of cow's milk daily (or 25 fluid ounces) would be getting 385mg of salt from that source alone - almost half the recommended maximum (one gram) for a baby up to a year old. One in eight of the children studied were fed only cow's milk, as opposed to breast or formula.