One in two children spend an hour or less outside per day, in contrast to prisoners who are guaranteed two hours in the open air every day, a global study has revealed.
A survey of 12,000 parents with children aged from five to 12 years old, in 10 countries, found almost a third of children play outside for just 30 minutes or less a day.
This research formed the basis of laundry brands' OMO and Persil's latest campaign - Free the Kids - Dirt is Good.
When a prisoner from a maximum security facility in America was told how little time children spend outside on average around the world, he replied: "Wow, that is depressing. That really is."
To mark the launch of the campaign, OMO and Persil released a film in which prisoners from Wabash Valley Correctional Facility in Indiana, America, talk about the importance they place on their daily outdoors time.
"You have time to feel the sun on your face, it's everything to me," said one inmate, who volunteered to take part in the project.
"It's the most important part of my day. I take my frustrations and problems and leave them out there.
"If it was one hour a day? I think that would build more anger, it would be torture."
"We were shocked when we discovered that children today were enjoying as little time outside as prisoners," said James Hayhurst, global equity director of OMO and Persil.
"That's why we decided to make 'Free The Kids', to bring this issue to life and to start a global conversation about the importance of play for children's learning and development.
"It has also prompted us to think about ways we can help families rediscover outdoor play, both at home and through schools."
'Free The Kids' has been launched in partnership with Sir Ken Robinson, a global speaker and author who specialises in creativity, innovation and education.
Sir Robinson will take the role of chair of the Dirt Is Good Child Development Advisory Board, alongside Dr Stuart Brown, founder of the National Institute of Play.
The Board will investigate the best ways to help children play, explore and get dirty every day, so that they can learn and develop to their full potential.
The campaign will be asking parents to share their views on play and sign their child’s school up to Outdoor Classroom Day via the newly created www.dirtisgood.com.
HuffPost UK blogger Karl Young has previously written about how important it is for children to play outside.
"Spending time outdoors with natural sunlight is vital to healthy sleep patterns, and we all know how important they are with children," he wrote.
"Spending time indoors watching television is ok, but the unnatural light from screens can have a detrimental effect upon your body clock, especially late at night."
Blogger Kirsty Morrissey said being outside should be a "right" for all children.
"Governments should ensure time outside is incorporated into education to guarantee no child is denied the access to nature that is so essential for their development," she wrote on HuffPost UK.
"It is too important to remain the privilege of children whose parents have the time, resources or inclination to take them out."