Urgent action is needed to stop children leading a “battery hen existence” during the summer holidays that is damaging their mental health, contributing to violence and ensuring they return to school in worse health than when they left, the children’s commissioner for England has warned.

In an interview with the Observer, Anne Longfield said radical measures were needed to restore the importance of play, such as overhauling play areas and parks, and encouraging GPs to recommend “play on prescription”.

She pointed to evidence showing that cardiovascular health and obesity levels deteriorate over the summer break as children stay indoors on computers and phones.

Longfield called for the funds raised by the government’s “sugar tax” to be used to ensure attractive play schemes were located in the right areas and gave children and parents a safe, exciting and affordable facility.

“We all remember how important the long school holidays were,” said Longfield. “But there is a sense that children are retreating into their homes or being limited to their homes, and we are seeing the consequences in terms of health, mental health and marginalisation from school and violence.

“Parents told me in the playground that if they hadn’t been there, the children would have been in the house in what was described to me as a ‘battery hen existence’ for so many kids – spending vast amounts of time during a hot summer online.

“A very straightforward, doable and increasingly evidenced way of tackling a whole range of these issues would be to have a major programme of investment in children’s play activities outside school and during school holidays.”

A study published last year by UKactive, a not-for-profit group of organisations that campaigns for better health, found that children were measurably less fit by the end of the summer holidays. The deterioration was considerably worse among children from deprived areas.

The primary school children in the study lost 80% of the fitness levels gained during term time. The poorest 25% experienced a drop in fitness levels 18 times greater than the richest 25%. The children’s body mass index worsened from an average of 17.64kg/m2 to 18.26kg/m2.

Research has also indicated that half of British seven-year-olds do not meet the chief medical officer’s minimum physical activity guidelines of at least 60 minutes activity every day.

Longfield, who will publish a report on the importance of play this week, said she had visited local schemes working with GPs. She suggested the “play on prescription” model could be widely adopted, once a proper network of play schemes had been established.

Facebook Twitter Pinterest Anne Longfield suggests locating adventure playgrounds in deprived areas. Photograph: Rex/Shutterstock

“Alongside all of the things that will be on a list of possible options for treatments, there would be something there that says you can buy a number of sessions in a [paid-for adventure] playground,” she said. “If children are there, they will be less anxious, out and about and improving.”

Proceeds from the sugar tax, expected to hit £240m this year, have been earmarked for school breakfast clubs and sports. However, Longfield said the money should also be used to boost play outside school time.

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She said she had visited adventure playgrounds that were already having a major impact. “If you could place some of these playgrounds in areas where there is real disadvantage, real poverty, concerns about violence, you are almost enabling children to reclaim that open space and benefit from all the free-range aspects of life that we all want them to have.”

Baroness Tanni Grey-Thompson, the former Paralympian and chair of UKactive, said: “We have built a world which suppresses our children’s natural instinct to be active, replacing it with sedentary lifestyles and screen addiction. The holidays should be spent playing with friends but for many children it has become an unhealthy, unstimulating and even lonely time – damaging their physical and mental wellbeing.

“We must make physical activity and play a public health priority for all children and young people, with practical solutions to make activities more accessible and appealing.”

Sarah Wollaston, the Tory chair of the health select committee, backed the calls. “Physical activity and play are enormously important to children’s physical and mental health,” she said. “Providing these facilities may save money down the line. It is fantastic value in avoiding the costs later on of poor mental and physical health.”

A government spokesperson said: “We are fully committed to ensuring that young people and their families have clear opportunities for physical activity and are determined to halve childhood obesity by 2030.

“Our world-leading childhood obesity plan will help children to exercise more and reduce their exposure to sugary and fatty foods, backed up by £40m from Sport England to encourage children and families from lower socioeconomic backgrounds to get active.

“We’re also investing £300m to work with schools and colleges to help promote, protect and improve children and young people’s mental health and wellbeing.”