Pureed products, canned food items, are most popular in the West. But a UK expert has warned that they could prove harmful to children. Purée is a general term for food, usually vegetables or legumes, that have been ground, pressed, and/or strained to the consistency of a soft paste or thick liquid.

The term comes from French, where it meant purified or refined. Infants should be fed exclusively on breast or formula milk for the first six months, then weaned onto solids. If not, it is feared they could lose out on vital nutrients derived from breast milk, which protect against common infections and allergies, says Gill Rapley, deputy director of UNICEF UK's Baby Friendly Initiative.

Spoon-feeding them pureed products could also delay their chewing ability, cause them to become fussy eaters and increase the likelihood of constipation. The warning comes after research backed by the World Health Organisation (WHO) showed that feeding babies pureed food was unnatural and unnecessary. Four out of five babies aged between four and twenty months now rely on the tinned and jarred products, many of which are organic or made with fresh local ingredients to increase their appeal to parents.

The pureed baby food industry in the UK is now worth more than £450 million - compared with £191 million in 1989. Mrs Rapley said: "Parents often think that their babies need something more than milk when they get to four months or so. "But scientists and government advisors now agree that this isn't the case.