The continuing failure of parents to ensure treatment for their obese child could be considered medical neglect when the child is suffering, or is at high risk of suffering, associated severe health problems.

Clinicians already have a legal requirement to contact welfare authorities when parents fail to follow medical advice in the treatment of other illnesses, such as parents who reject medication for a HIV-infected child, or who refuse a life-saving blood transfusion for a child on religious grounds.

Writing in the Medical Journal of Australia , doctors at the Children's Hospital at Westmead say the growing prevalence of severe obesity is leaving many health workers unsure if they should notify child protection workers when parents fail to follow medical advice.

"We argue that in an extreme case, the notification of child protection services may be an appropriate professional response," pediatric obesity experts Dr Shirley Alexander and Professor Louise Baur wrote.

Dr Alexander said the multidisciplinary team of specialists at the Children's Hospital at Westmead who look after cases of extreme obesity had decided to notify the NSW Department of Community Services if parents were unwilling or unable to co-operate with medical advice.

"The child may have insulin resistance and you've put them on medication to help prevent diabetes and the parents disagree with giving their child medication, or you show them evidence that children are at a higher rate of obesity if they have a TV in their bedroom, but the parent refuses to take the TV away," Dr Alexander said.

The article, published yesterday, described the case of a four-year-old girl, Jade, who was 110 cm tall and weighed 40 kilograms.

She had associated health problems including a fatty liver, hyperinsulinaemia and obstructive sleep apnoea.

Her separated parents let her watch up to six hours of TV every day, allowed her eat whatever she wanted and regularly failed to turn up for appointments with the hospital's dietitians and other health professionals.

After 12 months her weight had increased and Jade had become hypertensive (high blood pressure) and violent.

The hospital notified DOCS and Jade was admitted to hospital, where with a program of daily physical activity and a healthy diet, she lost three kilograms in two weeks.

After her discharge, the authorities insisted on supervised visits with her father and community health workers visited the mother to help her learn to buy and cook healthy food, and Jade lost another dress size.

Dr Alexander said while placing children in care was a sensitive issue, notifying child protection workers may lead to other forms of intervention, such as financial help to buy healthy food, or the drawing up of "responsibility contracts".