Ministers are to order schools to double the amount of sport and physical education taken by children.

Under government proposals, to be announced next month, pupils will be given the right to four hours of physical education per week.

Tony Blair will unveil the plan with Tessa Jowell, the culture secretary, and Charles Clarke, the education secretary, on December 7.

The prime minister is said to see the proposal as a key component of the "opportunity agenda" for Labour in its manifesto for the general election.