Researchers from Loughborough university believe that the Department of Health's plans to draw up a "fat map" for children in England could be counter-productive. The mass screening of Body Mass Index (BMI) in five to 11-year-olds, designed to alert parents to child obesity, is likely to increase anxiety among pupils, they say.
The report by Emma Rich, John Evans and Rachel Allwood, from the university's school of sport and exercise sciences, also questioned the accuracy of BMI testing.
According to DoH figures for 2004, a third of boys aged two to 15 are overweight or obese, compared with 24 per cent in 1995. Among girls of the same age, the figure is 35.1 per cent compared with 25 per cent a decade earlier.
Dr Rich said: "The broad message from this government on health and obesity is one that targets every aspect of education, from changing lunch menus and removing vending machines to giving parents advice.
"But, because of the complex relationship between health and weight, this is making schools accountable for something they may not be able to control.
"We risk ending up with a fat league, which reinforces the judgemental nature and pressures of the exams culture and league tables that we already have in schools.
"These new health imperatives create a whole new set of moral judgements, that thin is good and fat is bad. The implications are potentially very damaging for children psychologically and could lead to bullying."
Primary care trusts were instructed by the Government in January to screen all children in England between Years 1 and 6, during the summer term.
Dr Rich said: "In many schools children are being pressed to become increasingly conscious about their body weight, shape, diet and levels of exercise. This can inadvertently cause anxiety about weight, the food they eat and appearance which, in turn, can lead to eating disorders.
"Some studies show that people who are overweight according to their BMI are actually healthier than those who are thinner. Appearance, shape, size and weight might not be the real issue."
A DoH spokeswoman said: "The guidance issued in January ensures that the data collected is consistent and accurate across the country and also that PCTs have thought through issues of stigma, bullying and parental consent.
"The data will allow PCTs and schools to plan and evaluate services to tackle obesity and will allow them to be performance managed against an obesity indicator."
The department has not set specific targets.