Children in reception class, who are aged four to five, and children in year six, aged 10 to 11, had their size recorded as part of the National Child Measurement Programme.

The measurements, recorded by the Northamptonshire Primary Care Trust, were taken of 88 per cent of reception class children and 64 per cent of year six children.

Of those measured, 28.6 per cent of year six pupils were obese or overweight, along with 22.2 per cent of reception children.

The results, which are slightly better than the national average, are available to parents on request, but now Health Minister Ivan Lewis has said parents should automatically be informed.

Mr Lewis said: "Research shows that most parents of overweight or obese children think that their child is a healthy weight. This isn't about pointing the finger and telling parents that their children are overweight; instead it's about equipping parents with the information they need to help their children live healthier lives."

A PCT spokesman said the authority would consider the best way of putting the guidance into practice and said a combined approach was needed to tackle the problem.

He added that a group of health professionals, supported by a dietician and weight management specialist, is the way to deliver services across the county. This will include programmes within GP practices.

Work with Northamptonshire Sport and Cycling England could increase chances for activity.

For details of the survey, log on to www.ncmp.ic.nhs.uk/results.asp