An Australian study has found more than half of baby bottles have inaccurate or missing markings, with one in five failing world standards.

Parents could be overfeeding their babies because more than half of all baby bottles sold in Australia have inaccurate measurements, a study shows.

Experts fear that the lack of accurate measurement markings on the bottles could cause health problems for babies and put them at risk of becoming obese.

Researchers at Western Sydney University's School of Nursing and Midwifery bought and tested the entire range of baby bottles available for sale in Australia.

Of the 91 bottles, `57 per cent had inaccurate or missing volume markings, with 40 per cent missing at least one marking required to make up infant formula as per product instructions.

One in five had at least one marking that was so inaccurate it failed international standards.

This means parents could be making under-concentrated or over-concentrated formula.

"There's potentially some serious risks at the most extreme end," Adjunct Associate Professor Karleen Gribble, who led the research team, told AAP on Tuesday.

"For most babies it's not likely to be life threatening but for a lot of babies it will cause problems like constipation, it will exacerbate reflux and it could actually contribute to overweight and obesity."

She said disposable plastic liner system bottles were "particularly alarming".

"Those bottles are manifestly dangerous for babies because some of them are 45 per cent inaccurate," Assoc Prof Gribble said.

For example a parent could pour water up to the 100mL line but is actually only pouring in 55mL of water because the marking is inaccurate.

"That would result in really concentrated infant formula which in a young baby, a premature baby or a baby who'd been sick with diarrhoea, it could potentially be fatal," she said.

Most brands have at least one bottle with inaccurate markings and more expensive bottles were just as likely to be inaccurate as cheaper products, the report found.

Assoc Prof Gribble said there is an urgent need to implement an enforceable Australian standard to avoid harming babies.

"Infant formula is actually a really tightly-regulated product, but if it can't be made up as instructed because parents are unable to accurately measure water then what's the point?" she said.
"It's a failure of the system."

Their findings were published in the journal of Maternal and Child Nutrition.