Toddlers fed a diet of junk food can suffer lasting damage to their brainpower, researchers warn.

Children who eat more chips, crisps, biscuits and pizza before the age of three have a lower IQ five years later, a study showed.

The difference could be as much as five IQ points compared with children given healthier diets with fruit, vegetables and home-cooked food.

But even if their diet improves, it could be too late as the ill-effects can persist for a lifetime.