Dr Tam Fry, chair of the Child Growth Foundation, has dismissed this year's weigh-ins, which targeted children in reception and year 6, as "fundamentally flawed" because half of the children escaped the scales because of a shortage of nurses or lack of school cooperation.
In anticipation of next year's official review of the project, Dr Fry, in conjunction with the School and Public Health Nurses Association, is calling for sweeping reforms to ensure the difficulties that dogged this year's pilot don't result in further chaos.
In a report to be submitted to the Department of Health next month, he will demand the removal of the parental consent clause plus training to enable classroom assistants to take over duties from nurses. Dr Fry argues that widespread opting-out together with a lack of funding had produced false statistics.
"In my local borough of Hammersmith and Fulham only 48 per cent of targeted children were weighed," said Dr Fry, who helped draw up the obesity measurement guidelines.
"There is a shortfall of school nurses and parents of obese or overweight children are allowed to withhold consent. Let nurses get back to their job.
Children will respond much better to teaching assistants they know than some stranger telling them to strip."
The report anticipates the first comprehensive survey of the weigh-ins, being compiled by the Department of Health. The Government will be lobbied to mirror practice in north Birmingham Primary Care Trust where weigh-ins are combined with numeracy lessons.
Sharon White, professional officer at the public health nurses assocation, said many nurses feared the drive was taking qualified staff away from crucial child protection duties, and sexual and mental health work. She said that the initiative had been introduced without funding, leaving nurses "exhausted, overstretched, overwhelmed and under appreciated".
Helen Ross, a school nurse team leader from a primary care trust near London, said that ten extra staff including health visitors and administrative workers had to be drafted in to complete the programme which in her area covered 84 schools in two weeks. She also complained that no action was taken on problems.
Jayne Duly, lead professional for school nursing at South Derbyshire primary care trust, said many schools had been uncooperative, staging weigh-ins in "grotty corridors" and even failing to obtain consent from parents.
Nurses reached only 67 per cent of target children out of a possible 7,500.
Ms Duly said: "Quite a few schools didn't play ball. They need to do as they were asked."
The weigh-ins were introduced this year as part of a government strategy that aims to halt the rise in childhood obesity by 2010. They have been criticised by health professionals for encouraging eating disorders.
Bruni De La Motte, national officer for education staff at Unison, said:
"This is not a job for teaching assistants. It's not just weighing, it's deciding what will happen next if you find an obese child. It's a health initiative."
FATS AND FIGURES
100: The percentage of Year 1 and 6 children targeted by the government weigh-ins.
48: The percentage of those children reached in some areas.
2 million: The number of overweight children in the UK.
700,000: The number of obese children in the UK.
1 million: The number of children who will be obese in 2010 by current trends.
100: The record number diagnosed with type 2 diabetes last year, a strain normally seen in middle-aged adults.
2010: The year by which the Government has pledged to halt the year-on-year rise in childhood obesity.