Neil Armstrong, professor of health and exercise science at Exeter University, called them "short-sighted". If children did not learn the basic motor skills - throwing, catching, running, jumping, skipping - aged between seven and 11, they were unlikely to do so later on, he said.
At secondary level when they grow faster, they are more awkward and clumsy so it is difficult to learn those skills. It was important to establish a habit of taking exercise early on which would carry into adulthood.
"We might have a more literate and numerate society, but a less healthy one, and I'm not sure that's what David Blunkett wants," said Professor Armstrong.
Pat Smith, general secretary of the National Council of School Sport, agreed. He pointed out that few children walked to school, played in parks or streets as they used to. Exercise was usually organised and school-based so it was vital that primary schools should instil habits for an active lifestyle.
Mr Smith was disappointed that the Government appeared to be reneging on its manifesto commitment to PE and sport. His association, he said, would still be pressing for a minimum of two hours a week for the subject.
But critics were aware of the tremendous pressure on teachers with an overloaded curriculum. John Evans, professor in physical education at Loughborough University, said they had been subjected to a dreadful experiment of social engineering. The new guidelines could result in wide differences in practice.