nicki lerczak's List: Raising Responsible Kids

The report's author, Dr William Bird, the health adviser to Natural England and the organiser of a conference on nature and health on Monday, believes children's long-term mental health is at risk.

He has compiled evidence that people are healthier and better adjusted if they get out into the countryside, parks or gardens.

Stress levels fall within minutes of seeing green spaces, he says. Even filling a home with flowers and plants can improve concentration and lower stress.

"If children haven't had contact with nature, they never develop a relationship with natural environment and they are unable to use it to cope with stress," he said.

"Studies have shown that people deprived of contact with nature were at greater risk of depression and anxiety. Children are getting less and less unsupervised time in the natural environment.

"They need time playing in the countryside, in parks and in gardens where they can explore, dig up the ground and build dens."

The report, published by Natural England and the Royal Society for the Protection of Birds, also found that children's behaviour and school work improve if their playground has grassy areas, ponds and trees.

It also found evidence that hospital patients need fewer painkillers after surgery if they have views of nature from their bed.