The cost of injury on duty payments to former police and prison officers in Northern Ireland has soared to more than £500m, the UK Audit Office has said.

The scale of claims is significantly greater than in England.

One award in 2018-19 dated back 25 years and cost £429,000 in arrears alone.

UK auditor and comptroller general Kieran Donnelly said: "Substantial changes are necessary if the schemes are to be affordable in the future."

The current review of the UK Prison Service scheme should be joined by a similar, fundamental review of the PSNI scheme, the independent watchdog added.

He said: "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.

"The end-to-end process for the PSNI scheme needs to be simplified and streamlined, with reconsideration given to the respective roles of the PSNI, the Policing Board and the Department of Justice.

"In the interim, the public bodies involved should take action to address the most urgent issues."

Both schemes have seen costs increase substantially over the last five years, with £33.9m spent by PSNI and £2.3m by the Northern Ireland Prison Service in 2018-19.

Total liabilities are estimated at £488m for the PSNI and £53m for the Prison Service.

The scale of claims in Northern Ireland is significantly greater than in England.

The Policing Board receives an average of 12 claims per week.

London's Metropolitan Police Service, with more than 30,000 officers, receives around 20 applications each year.

No police service in England has more than 650 injury on duty awards in payment, while there are more than 2,800 in Northern Ireland, the Audit Office said.

A Policing Board statement said: "The board is well aware of the challenging and complex nature of this area of work having previously commissioned and published a comprehensive review of the Police Pension Injury on Duty Scheme in 2014.

"At this time a range of recommendations including the need for legislative reform of the governing regulations and design of a simpler scheme were made.

"Given the significant cost implications and scale of the administration of the current Police Injury on Duty Scheme, the Board fully supports the NIAO view that reform and change is urgently needed and hopes this can now be progressed expeditiously."

In March last year, there were 2,881 injury awards in payments for former police officers and 181 for former prison officers.