An Australian couple have pleaded guilty after their vegan diet led to their malnourished infant developing severe rickets and bone fractures.

The couple, who cannot be named for legal reasons, fed their 19-month-old daughter restrictive meals of just toast, oats, bananas and rice milk. As a result she developed rickets, a degenerative disease that leads to soft and weakened bones.

This was only discovered after she was admitted to hospital earlier in the year after suffering a seizure. At the time, doctors said she didn't talk or crawl and her skeleton was covered in fractures.

Her mother told hospital staff the family followed a strict vegan diet, which they wanted to keep their daughter on. She also wanted to prevent the hospital feeding her daughter soy as it was full of "hormones".

After an investigation, doctors found the girl had no birth certificate, hadn't had any follow-up checks after she was born and lacked immunisations.

Her levels of vitamin D - which can cause bone disease if too low - were "undetectable" and she had severe deficiencies in calcium, phosphate, vitamin B12, vitamin A, iron and zinc.

Police charged the couple over their daughter's condition. During their court appearance, they argued the girl was "a fussy eater", however pleaded guilty to failing to provide for a child and causing serious injury.

The girl and her siblings have been taken into foster care and the couple face sentencing in January.

Newshub.