New advice from the government says children under five-years-old should exercise for at least three hours a day, as part of an initiative to fight obesity.

Parents will be told to take toddlers on walks of up to 15 minutes – especially for routine journeys such as to nursery – while they are encouraged to give babies activity mats and take them swimming.

England’s chief medical officer, Sally Davies is reported by the Daily Mail to have said: “I think there are parents who are not aware how important it is for their children to be physically active.

“This matters to your child now, to their development through childhood and adolescence and to their disease profile in middle-age and later life.”

Recent research has linked early exercise with both physical and mental health. According to the NHS, almost a quarter of kids aged four to five are either overweight or obese and experts say that 63 per cent of children could fall into this category by 2050.

But Professor David Haslam, GP and chairman of the National Obesity Forum, criticised the government’s plan. He told the Daily Mail: “It is a little bit naïve to come up with guidelines when what is needed is safer streets and more parks and more availability for exercise for toddlers.”

The guidelines, which are to be issued this week, are called “Start Active, Stay Active” and follow claims that Britain’s children are some of the laziest in the world. This is the first time the UK government has targeted under-fives in an anti-obesity drive.