More than £260 million is to be cut from Northern Ireland's policing budget over the next four years.
The prison service will have to find savings of just over £65 million.
The figures are in a draft budget proposal published by the Department of Justice on Thursday night.
The Police Service of Northern Ireland is asking the Treasury for additional emergency funding of £200 million to combat the dissident republican threat.
Most of the Justice Department budget is spent on policing and prisons, and they will bear the brunt of cuts outlined in the department's draft proposals.
The PSNI will have a budget of more than £3 billion during the next four years.
But it is also being asked to make savings of just over £260 million during that time.
The prison service will have a budget of more than £500 million for the next four-year period. But it will have to deliver savings of just over £65 million.