The government's chief medical officer has advised that children need to take more exercise.
Sir Liam Donaldson said in his annual report that the "harm caused by inactivity is very substantial".
He called for the government to implement health schemes in schools, such as the 'Bleep' test, which would provide a way of monitoring children's fitness levels.
However, Amy Schofield, editor of education and parenting website mychild.co.uk, argued that parents and carers should take responsibility for their children without government intervention.
She added: "We all need to take responsibility for educating our children on how they can stay fit and healthy and the best way is to lead by example."
According to Mr Donaldson, up to 70 per cent of adults in England are not taking the recommended amount of physical exercise.
The worry is that this is being passed on to young people as the chief medical officer's report shows that child fitness is falling by up to nine per cent a decade.