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

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 to nursery, chief medical officers will say.

The exercise guidance, to be issued this week, targets under-fives for the first time and comes amid growing fears over childhood obesity.

“For children that are not yet walking, there is considerable evidence that letting children crawl, play or roll around on the floor is essential during early years,” England's chief medical officer Sally Davies said.

“Play that allows under-fives to move about is critical and three hours a day is essential,” she was reported as saying yesterday.

“Other parents are very busy and may not see how important it is to get that prioritisation and balance right.”