Many contain high levels of sugar and some are promoted for use from four months of age – a time when babies should be on a diet of breast or formula milk.
Babies would need to eat twice as much shop-bought food to get the same energy and protein as meals cooked at home, researchers found.
The study, from the department of human nutrition at the University of Glasgow, said many weaning foods “would not serve the intended purpose” of giving a baby extra nutrients or a range of tastes and textures.
Current guidelines encourage weaning from six months of age, with babies fed only breast or formula milk before this time. But some parents choose to wean early and baby foods are often marked as “suitable from four months”.
Experts analysed all the baby foods produced by the main UK manufacturers – Cow and Gate, Heinz, Boots, Hipp Organic, Ella’s Kitchen and Organix.
Of the 479 items, 364 (79 per cent) were ready-made spoonable foods and 201 (44 per cent) were aimed at infants from four months. Some 65 per cent of the products were sweet foods.
The researchers said the typical calorie content of the spoonable foods was 282 kJ per 100g, almost identical to breast milk at 283 kJ per 100g of formula.
But purees and spoonable foods made at home were “more nutrient dense” than the shop-bought foods. Examples of homemade foods included chicken stew, beef with mash, stewed apple with custard and apple with rice pudding.
And while commercial finger foods contained more calories, they had a “very high” sugar content. The iron content of most of the foods was also lower than that found in formula.
Writing in the journal Archives of Disease in Childhood, the researchers said: “The UK infant food market mainly supplies sweet, soft, spoonable foods targeted from age four months.
“Most products are ready-made spoonable foods that are no more energy dense than formula milk, and are generally much less nutrient dense than homemade foods.”
The Department of Health recommends babies continue to receive breast milk or a pint of formula a day while they are being weaned, up to their first birthday.
The experts said many shop-bought foods are sweet, possibly to cater for babies’ inherent preference for sweet foods.
While shop-bought foods use fruit sugars to sweeten foods rather than added sugars, both probably contribute to tooth decay in equal measure, experts added.
A statement from Heinz said: “Generations of parents have trusted Heinz baby foods as safe and nourishing and which are specially prepared to meet babies’ nutritional needs with recipes that provide the right tastes and textures.”
A statement from Organix said it did not add vitamins and minerals to foods due to organic production rules.
The statement added: “An exception to these rules is where there are general food industry laws and regulations that supersede any organic rules.”
Nobody was available for comment from Hipp Organic.
Helen Messenger, a spokeswoman for Cow and Gate, said: “Our foods offer good quality nutrition tailored to meet babies’ needs and must comply with strict legal standards.”
Rosemary Dodds, senior policy adviser at the National Childbirth Trust, said: “Manufacturers have been dragging their feet, lagging behind current thinking and research evidence that babies don’t generally need solid foods before about six months. It’s time they stopped labelling foods ‘from four months’.
“If babies are spoon-fed pureed fruit and vegetables before this time, it can replace the nutrients from milk.
“Many parents do find jars of food convenient when they are out and about, but babies can eat family foods most of the time.
“Buying commercial baby foods is also much more expensive than using family foods.”