Almost one in three Victorian children is overweight or obese, sparking calls for the state to do more to reverse the worrying trend.

Victorian children are the fattest in the country, putting them at higher risk of obesity-related cancers, experts say.

Almost one in three Victorian children, or 216,600, are now overweight or obese, according to latest Australian Institute of Health and Welfare figures.

And childhood obesity rates are climbing higher than any other state, prompting calls from the Cancer Council Victoria for a state strategy to reverse the trend.

"If obesity rates continue to rise, we could be resigning our children to a lifetime of obesity-related illnesses including Type 2 diabetes, heart disease and 13 types of cancer," the council's Craig Sinclair said.

Childhood overweight and obesity jumped from 23 per cent in 2011 to 30 per cent in 2014, above the national average of 26 per cent.

Mr Sinclair said these children are much more likely to remain in these categories as teenagers and adults, potentially resigning them to a lifetime of obesity-related illnesses and cancer.

"According to these new figures, childhood obesity rates are actually going down in some other parts of the country. It's vital that Victoria does more to reverse this devastating trend," he said.

The Cancer Council wants the Victorian government to develop a strategy that includes public education, more access to nutritious foods and removing sugar sweetened drinks from state owned, managed or funded facilities.

The figures demonstrate the unhealthy environment children are exposed to daily, including junk food ads, according to the Obesity Policy Coalition's Jane Martin.

"It's time for a state strategy to address the health impacts obesity is having on Victoria, and a focus on tackling childhood obesity must be a priority," she said.