Parents of fat children have been warned they could be shamed into taking action to stop obesity. The government proposes to send letters to any parent whose child is found to be overweight. At schools across the country pupils will be weighed to see if they're a healthy size for their age and height. Some scientists say within the next forty years up to a quarter of all British children will be clinically obese. But critics of the announcement say sending one letter doesn't go far enough.