"This contributes greatly to the burden of growing anti-microbial resistance," said study leader Dr Rod James of the University of Melbourne.
The study shows there has been little improvement in prescribing since the widespread rollout of antibiotic stewardship programs at hospitals about two years ago.
However, Dr James was optimistic the review of more than 13,000 prescriptions at 152 hospitals would provide critical information to help improve practice.
"It's early days," said Dr Looke.
"This is a baseline. We should start seeing improvements. These stewardship programs have only recently started coming into hospitals."
Urgent action was essential, he said.
"We prescribe double the amount of antibiotics per head of population compared with the Netherlands, but health outcomes are similar in both countries.
"It's not as if the Netherlands aren't treating people with infections."
Australia could also learn from Scotland, which had set a 90 per cent target for appropriate prescribing.
He said people were entitled to ask their doctor if their antibiotic was necessary and what the consequences would be if they did not have it.
"It is always appropriate to ask what side effects might occur."
Resistance caused by over-use of antibiotics was a community issue, he said.
"Luckily Australia has not had huge problems like other countries.
"But we want to preserve the effectiveness of our antibiotics for the future.
"We don't want to be in a position where we can't do transplants or chemotherapy because of antibiotic resistance."
Australia needed to slash antibiotic use by a quarter, said Dr Janette Randall, chair of NPS MedicineWise.
This would bring it in line with the average for countries in the OECD (Organisation for Economic Co-operation and Development).
"With around 19 million prescriptions written in Australia every year, we are among the highest users of antibiotics in the developed world."
- AAP
