Teachers will also be encouraged to do more to promote competitive sports, under the plans which will be unveiled by the Liberal Democrats at their annual spring conference in Perth this week.
Labour’s coalition partners will push for the strategy to become Scottish executive policy in the wake of mounting evidence that a lack of exercise is contributing to rising obesity among Scottish children.
More than 90% of primary schools are failing to meet the executive’s own target of providing pupils with at least two hours of physical education a week.
A study by The Sunday Times last year revealed that most 11-year-olds receive just 76 minutes of exercise a week and more than one in 10 receive less than an hour.
Critics blame ministers for overloading the curriculum to the point where physical education is being squeezed out.
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The executive wants all schools to give children access to two hours of PE a week but this is not mandatory.
Scotland’s poor fitness levels and lack of a competitive sporting culture in many schools has been blamed by some for the country under-performing in football, rugby and athletics at an international level.
The Lib Dems, whose senior figures include Sir Menzies Campbell, a former Olympic athlete, and Donald Gorrie, a former Scottish sprinter, believe that sport improves physical and mental wellbeing as well as engendering a sense of national pride.
Senior party figures will say this week that PE should be compulsory in all schools until the end of the fifth year. They will also call for schools and sports clubs to do more to encourage the desire to win among young people.