At a conference in Edinburgh to launch the first Play Commission in Scotland, experts said children in industrialised nations were not getting enough "free play" away from adults and in unstructured environments.
While much of this social change is due to the fear of children being abducted or harmed, academics have identified a new trend - the McCann effect - which is increasingly a factor.
This is people's concern of being seen as poor parents if their children are allowed out of their sight. Madeleine McCann was abducted from a holiday villa in Portugal while her parents were dining with friends at a nearby restaurant.
The seminar also heard that Scottish Government research, based on a survey of parents, has found that nearly one in six children does not have anywhere to play. In deprived areas, this figure rises to one in four.
Play Scotland, the independent children's charity that organised the conference, has just received 10,000 from the National Lottery to set up the Play Commission in Scotland.
Chaired by Sue Palmer, the Edinburgh-based author of Toxic Childhood, and Kathleen Marshall, Scotland's Commissioner for Children and Young People, the commission will consult about the best way to improve play for children. Its recommendations will be presented to the Scottish Government next year.
At the conference, Dr Roger Hart, an expert in childhood development from the United States, said that allowing children to play unsupervised with their peers was an essential part of growing up.
He said a lack of such play could impair the personal development of children. It could impact on their confidence, affect the development of their imagination and stall their ability to deal with friends of the same age.
"We have become hyper-vigilant about children's safety but also hyper-vigilant about how they learn. We do not even trust children to play any more," said Dr Hart, co-director of the Children's Environments Research Group at the City University of New York.
More space had to be given over to allow "free play", where children create their own games and activities without the direction of adults: for example, leaving objects lying around a playground for children to play with and introducing nature into urban areas.
Dr Hart, who has written books with the charities UNICEF and Save the Children, said: "The Madeleine thing has been all over the world and I am certain it has built on that fear and it has also resulted in other stories [about child abduction being highlighted]."
Ms Palmer said the case had made parents more reluctant to let children play alone. "It is making it worse because parents are more anxious, but also children are more anxious," she said.
"If lion cubs stopped play-stalking, play-fighting, play-hunting, the species would die out.
"Play is how you learn to be a human being and, if it is being supervised by adults all the time, children are not learning the essential social skills, sense of independence and resilience, and you are storing up problems for the future. Parents think it is so important to keep them safe and keep an eye on them at all times, but in fact children need leeway to make mistakes."
Marguerite Hunter Blair, the chief executive of Play Scotland, said parents had a "disproportionate fear" of their children being abducted by a stranger. "I think the instant global coverage of Madeleine McCann gave you a disproportionate fear, even if your commonsense tells you otherwise," she said.
"You feel you will be badly judged by your peer group if you do not move to the new norms of being seen to pay more attention to your child."
Dr John McKendrick, from the School of Social Sciences at Glasgow Caledonian University, said high-profile child murders such as the Dunblane massacre and the James Bulger case have always fuelled parents' fears. "If you have a high-profile case in the media, parents will talk about it and thereafter that will influence their opinion," he said.
"We do need to start to appreciate that the perceived dangers out there do not match up to the reality."
Dr McKendrick cited government research that found almost one in six children did not have anywhere to play. He said Scotland needed to build more play areas in housing developments and make existing areas more child-friendly.
A Play Scotland report on provision for children found only 38 per cent of local authorities had a policy or strategy on play, and only 25 per cent offered children free access to leisure centres. It also showed a lack of playgrounds in urban areas, where the number of children per playground often exceeds the national average of 255.
Ms Marshall, the Children's Commissioner, said: "Parents can't be blamed for wanting to keep their children safe. The worldwide scope of the media means parents today are regularly exposed to graphic details of very rare tragedies affecting children. As a society, we need to take steps to support parents and give them the confidence to allow their children the freedom they need to explore their environment and engage in stimulating activities. Some communities, for example, have introduced play 'rangers' who are available to support children to use public space safely and responsibly. Scotland needs a play strategy that will tackle these issues."
60 NEEDLESS DEATHS A YEAR
THE deaths of more than 60 children in one year could have been prevented if Scotland had a better approach to child safety, European experts have claimed.
A "report card"
looks at areas including poisoning, cycling and drowning. The biggest improvements are in road safety. But it says that if Scotland achieved the same standards as Sweden - Europe's best performer - 62 deaths would have been prevented in 1991, the year of the study. The country's Child Safety Report Card, published by the European Child Safety Alliance, says "stronger leadership from government is required".
A Scottish Government spokesman said it takes the issue of child safety extremely seriously.
'FEAR USED AS AN EXCUSE'
MANY parents use the fear of crime as an excuse for not making time for their children to play outdoors, it has been claimed.
Parenting experts say a "culture of fear" has exaggerated the dangers youngsters face. However, they believe over-protection of children may lead to them becoming less streetwise.
Kristina Woolnough, head of support group Parents in Partnership, said: "Everybody lives such busy lives these days. Parents find they are running from pillar to post and have so little time to let their kids out to play. This has the effect of shrinking their imaginations, and making them less confident.
"There is a culture of fear, but that is too often used an excuse by people who are simply too busy."