Children under the age of five should exercise for at least three hours a day, new Government guidelines will suggest this week.

Babies should be taken swimming and play on "baby gym" mats, while toddlers should walk for at least 15 minutes of routine journeys such as going to nursery, chief medical officers will say. The exercise guidance targets under-fives for the first time and comes amid growing fears over childhood obesity.

According to NHS figures, almost a quarter of children aged four and five are overweight or obese. Experts predict that by 2050, this could rise to 63 per cent.

Sally Davies, England's chief medical officer, said evidence shows under-fives, including those too young to walk, need exercise – even if it is just rolling on the floor.