Natural England is encouraging children to visit nature reserves and farms
Nervous parents are making the countryside "out of bounds" for their children, a survey has suggested.
Natural England produced the survey, called One Million Children Outdoors, to launch a project encouraging children to visit the countryside.
It found fewer than 10% of children played in natural places, compared with 40% of adults when they were young.
A total of 1,150 adults and 502 children took part in the online survey conducted by England Marketing.
The organisation said children were being denied the independence and experience which came from exploring the natural world.
Natural England's Childhood and Nature survey found only 24% of those with an area of nature near their homes visited it weekly.
More than 70% of children said they were supervised wherever they played (that total rose to more than 80% when they played in natural places) and 81% said they would like more freedom to play outside.
'Independence and freedom'
The majority of parents - 85% - said they would like their children to be able to play in natural spaces unsupervised.
But they said fears of strangers and road safety prevented them from giving much freedom to their offspring.
As part of Natural England's One Million Children Outdoors project, farm visits and visits to national nature reserves will double for school-aged children.
An interactive wildlife gardening website is being launched and it will promote a nationwide marine conservation campaign.
Poul Christensen, acting chair for the organisation, said: "Children are being denied the fundamental sense of independence and freedom in nature that their parents enjoyed.
"Our research shows that contact with nature has halved in a generation and that the overwhelming majority of children now want more opportunities to play outdoors.
"Whether through pond-dipping or tree-climbing, nature-based activities can play an important role in the educational and social development of children."
He added: "The natural environment is there to be explored by children, it is their right. The memories they collect from it stay with them as adults and inspire them to pass on a healthy environment for future generations."
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Chris Packham, naturalist and television presenter, also welcomed the new programme.
He said: "If a generation becomes detached from the natural world, it is in danger of becoming indifferent and whilst some skills are learnt in the classroom, others only come from being knee-deep in mud and elbow-deep in frog spawn.
"It is these early years of inspiration that set in motion a life-time passion. Today's young explorers are tomorrow's naturalists, biologists. If they don't learn how it works, how will they look after it for the future?"