Mo Farah and more than 70 leading UK sporting bodies have demanded the government rethink potential £120m cuts to school sports in England, after a clash between two departments over the funding.

The Guardian reported earlier this year that the Department of Health and Social Care had intended to cut its entire £60m contribution to school sports, though ministers have since said they intend to rethink the level of cuts.

The Department for Education had also proposed an additional £60m cut – though ministers have said it would come from efficiencies from a new partnership model.

The 76 sporting bodies, which include ParalympicsGB, British Rowing and Aquatics GB, said there was “deep concern” in the sporting world over the proposed cuts.

Farah, an Olympic gold medal long-distance runner who is the national school sport champion, said he was “really concerned about rumours suggesting the government is going to cut funding for school sport. There is so much optimism across sport and education about the potential impact a new structure could have.

“We can’t risk this huge opportunity to improve PE and school sport being wasted for short-term savings when in the long-term it will damage children’s happiness and health. I hope the government listens to leading voices and quickly confirms current spending levels on PE and school sport will be maintained.”

A funding decision is expected to be announced as soon as next week. But in a letter to the health secretary, Wes Streeting, and the education secretary, Bridget Phillipson, coordinated by the Sport and Recreation Alliance, the sporting organisations said the new model announced by Labour could not be underfunded.

“Quality, inclusive PE and school sport is critical to our children’s health and wellbeing, academic success and sense of belonging in school,” the letter said.

“It provides the essential foundation for all children and young people to be active throughout their lives and, for some, to become the next generation of sporting stars.”

The letter warned that any reductions in funding “risk having a hugely detrimental effect on children’s health, wellbeing and opportunity” and added that there was significant uncertainty in the sector over how the new partnerships model would work.

“The uncertainty created by the lack of clarity on future funding is already having an impact, with many schools and sector organisations unable to commit to longer-term planning beyond the end of this school year,” it said.

Others who have signed the letter include British Cycling, England and Wales Cricket Board, the Lawn Tennis Association and British Gymnastics.

Though the bodies said they were supportive of the new PE partnerships model for schools, they said it could be delivered only with the existing level of funding.

The letter said: “A reduction in funding risks setting it up for failure before it has got off the ground and undoing much of the progress made in recent years. There is a real opportunity to build on the world-leading PE and school sport system introduced under the last Labour government and we believe it is essential it is given the right resources to have the best chance of success.

“Reducing funding would run counter to these aims and ultimately negatively impact those who stand to benefit most.”

The alliance’s chief executive, Lisa Wainwright, said: “At a time when children’s physical and mental wellbeing must be a national priority, a reduction in funding for PE and school sport would be deeply counter‑productive.

“We are therefore deeply concerned to hear that funding may be reduced and alongside our members, including national governing bodies we represent, we are urging ministers to provide clarity that investment in PE and school sport will be maintained, ensuring every child, regardless of background, has the opportunity to be active.”

The changes to PE from next year proposed by Phillipson will replace the sports premium with a PE and school sports partnership network from the next academic year, mandating two hours a week of physical activity and building partnerships with schools and local sports clubs.

It will also require schools to advertise their sports offering publicly to parents and is intended to address regional disparities in sports offerings.

The proposed cuts came despite growing concerns about inactivity among children contributing to obesity and lasting health inequalities. Sporting bodies including Sport England have been highlighting a growing problem with inactivity among children, with fewer than half of children meeting the chief medical officer’s guidelines.

Government figures published last year confirm a significant decline in the number of hours allocated to PE in secondary schools, down by nearly 4,000. The most significant drop in hours has affected 11-14-year-olds – the group that is also experiencing the fastest growth in obesity.