The government was accused of being "prissy" and "namby- pamby" yesterday after it told health trusts to avoid using the word "obese" when telling parents their child is overweight.

The Department of Health is urging all primary care trusts (PCTs) to automatically tell parents their child's height and weight as part of a national measuring programme. But ministers do not want the word "obese" to be used in the letters home after research showed it "shuts people down". Instead, the heaviest children should be referred to as being "very overweight", they said.

Dr Will Cavendish, director of health and wellbeing at the Department of Health, said it was important parents received information which helped them take action.

"We have not banned the word obese but we have chosen not to use it," he said. "There's no point giving them a letter that doesn't have any impact on their behaviour."

But Tam Fry, board member of the National Obesity Forum, said it was important to be frank with parents.

Experts in the US had also suggested banning the word obese but had now changed their minds and decided the word was necessary, he added. "I find this particular line from the government tip-toeing through the daffodils," he added. "The Americans have gone back to using the term because it's the kind of shock word that makes parents sit up and take notice.

"It's a nasty word but by god it should sound alarm bells in parents' minds. I find this whole approach from the Department of Health a bit prissy and namby-pamby."

Under yesterday's guidance, parents will receive letters detailing their child's weight and height. Children will not be given the results to take home in a move designed to prevent them being bullied by other youngsters.

Parents of overweight children will have to be proactive in seeking help, with the letter advising them to contact their GP, school nurse or practice nurse for further information. The letter will detail the child's height and weight, stating the child is underweight, a healthy weight, overweight, or very overweight.

The analysis will be based on a calculation of the child's body mass index (BMI), although parents will not be told the BMI over fears they could find it confusing. The guidance to PCTs says research shows parents "disengage with the term obese' and believe that it does not relate to their child". It said studies on what should be included in the letter "explored the use of the word obese' and the vast majority of parents were adamant that this should not be used, especially when discussing children".