The Department of Health is considering plans to send warning letters to parents if their children are found to be obese.

The routine weighing of primary school pupils was reintroduced in England and Wales two years ago.

Under the National Child Measurement programme, children are weighed at five and ten - when they start school and when they leave.

Parents are only informed of the results if they request them, but from next school year they will be encouraged to do so and directed to a new website helping them calculate how much their children should weigh.

Health secretary Alan Johnson is reported to be preparing to go further and insist that letters are sent to all parents as a matter of course.

A spokesman for the department said: "Tackling child obesity is a government priority and the weighing and measuring programme is an important element of this.

"The programme is a vital part of engaging with children and families about healthy lifestyles and weight issues.

"We need to take this further and help parents to understand the importance of healthy weight for their families and support them to make lifestyle changes.

A Foresight report published last week warned that a majority of Britons will be obese by 2050, if weight gain continues at its current rate.