Parents of primary schoolchildren will start getting letters next month telling them how fat their children are under Government plans to tackle childhood obesity. But however much they weigh, no child will ever be described as “obese”.

The Department of Health faced criticism yesterday for a “prissy” approach to tackling obesity after it said that it did not want the term “obese” included in the letters.

The department said that research had shown that the term was a turn-off, so instead it will use the term “very overweight” for those children whose body mass index exceeds 30, in an attempt to enlist parents’ support.

Primary care trusts (PCTs) have been given a detailed set of instructions, and a sample letter, explaining how to convey to parents the results of the National Child Measurement Programme.

Among other forbidden words is “exercise”. Will Cavendish, director of health and wellbeing at the department, said that this, too, conveyed an unhelpful image to parents. Being “physically active” is preferred.

“We haven’t banned the use of the word obese, we just haven’t used it,” he said. “The word just shuts people down. This is not an academic exercise - there’s no point in giving parents a letter than doesn’t have an impact.”

But Tam Fry, of the Child Growth Foundation, said that it was “prissy” and “namby-pamby” not to use the right word. Experts in the US had also suggested banning the word obese, he said, but had since changed their minds and decided that the word was necessary.

“I find this particular line from the Government tiptoeing through the daffodils,” he said. “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.”

It has taken the department three years, and a change in the law, even to get this far in tackling the growth of childhood obesity.

Parents will still be allowed to opt out from having their children weighed and measured when they enter primary school at 4 to 5, and again in Year 6 (aged 10 to 11).

Last year, PCTs managed to weigh 80 per cent of children at these ages. The target next year is 85 per cent. But there is a fear that those who opt out will be the parents of fatter children, so the results will still fail to capture the full scale of the problem.

The plan is that all parents, whatever their children weigh, will get a letter telling them the results. This will include height and weight, and a mark on a scale running from “underweight” through “healthy weight” to “overweight” and “very overweight”. The scale measures body mass index, although the term is not used for fear that parents will find it confusing.