Prison costs are rising at a rate exceeding all other government expenditure.

A new report from the Office of the Prime Minister’s Chief Science Adviser's revealed we have one of the highest rates of incarceration in the OECD - even though crime is dropping.

The report blames a culture of tough-on-crime policies, rather than focusing on prevention and mental health and recommends switching focus from being tough on criminal acts, to prevention and early intervention.

Restorative justice campaigner Kim Workman told Kate Hawkesby we're spending about $100,000 per prisoner per year.

"Even the most expensive intervention, things like multi-systemic therapy, still come out as less money than what we're spending."

Workman says there's no relationship internationally between prison numbers and crime rates.

"Imprisonment rate is usually a political response - the government decides how much money it wants to spend punishing people."

LISTEN ABOVE AS KIM WORKMAN SPEAKS WITH KATE HAWKESBY