Schemes that provide payments to former PSNI and prison officers who sustained injuries while on duty are not fit for purpose, a report has said.
It warns that substantial changes are needed if the schemes are to remain affordable in the future.
The rate of claims here is far greater than in England, auditors found.
Injury on duty awards are made to former police officers and prison officers for injuries sustained while on the job.
The PSNI and the Prison Service schemes are two of the largest of their type in Northern Ireland.
Both schemes have seen costs soar over the last five years, with £33.9m spent by the PSNI and £2.3m by the Prison Service in 2018/19.
Total liabilities are estimated at £488m for the PSNI and £53m for the Prison Service, the Northern Ireland Audit Office said.
Comptroller and Auditor General Kieran Donnelly said: "Substantial changes are necessary if the schemes are to be affordable in the future.
"The current review of the Prison Service scheme should be joined by a similar, fundamental review of the PSNI scheme.
"Both reviews should provide clarity on the aims of the schemes and how these will be accomplished and how appropriate checks and balances can be established."
Today's report reveals the scale of claims in Northern Ireland is significantly greater than in England. The Policing Board receives an average of 12 claims per week. The Metropolitan Police Service, with over 30,000 officers, receives around 20 applications each year.
No police service in England has more than 650 IoD awards in payment, while there are more than 2,800 in Northern Ireland.
The PSNI scheme is complex and challenging to administer, the report adds.
While the PSNI is responsible for the budget, the Northern Ireland Policing Board is responsible for the overall administration of the scheme and the Department of Justice is responsible for the legislative framework and for co-ordinating medical appeals.
Auditors also found the payment of injury awards is not always equitable. Someone of pension age with an IoD award could earn more than another officer with a retirement pension.
The report said backdated awards have a significant impact on the spend as they involve payment of arrears of the award from the date of the injury.
One example dated back 25 years and cost £429,000 in arrears alone.