The PSNI could be left "on its knees" if up to 1,000 officers are cut from its ranks by 2025, according to the Police Federation of Northern Ireland.
The PFNI represents officers in place of a union, which police forces are not allowed by law to have.
It comes after a letter to politicians from the Chief Constable Simon Byrne, in which he confirmed officer numbers may drop to about 6,000 in three years time.
Read more: "Officers are getting burnt out" - PSNI officer opens up on low morale in police ranks
That number was meant to be at 7,5000 under the terms of the New Decade, New Approach agreement, but Stormont parties have never been able to follow through and it currently sits at around 6,800.
The PFNI Chairman Liam Kelly said it was a worrying time for officers of all ranks.
“We haven’t been in such a parlous position in the 21 years the PSNI has been in existence. Incalculable damage will be done," he said.
"What we are now seeing is a threat to the everyday ability of the Service to maintain essential services."
He said the blame for the situation was not be laid at the feet of serving officers and instead said it was a failure of political leadership.
“No budget, cost overruns, a freeze on recruitment, no pay settlement, a brutal cost-of-living crisis and scores of officers leaving for work elsewhere are the ingredients of a crisis never before experienced," he added.
“The Chief Constable says it will result in what he calls ‘a smaller, less visible, accessible and responsive police service.’
"I agree, but even that description doesn’t go far enough. The full range of services will go into reverse."
Mr Kelly said it was vital that the Chief Constable expanded on what he said in his letter, laying out exactly how the service would operate if numbers reduced drastically.
He also claimed that if local politicians could not find a way to re-establish governance, the matter should be taken out of their hands.
"Boycotting the Executive and making the Assembly a running joke undermine politics and destroy what little credibility that is left," he said.
"Failure at local level must mean intervention by Westminster.
"A budget is required and only Westminster can do that in the event of political meltdown in Northern Ireland."
READ MORE:
- Police Federation Northern Ireland exploring industrial action for PSNI officers
- PFNI complain of "total disregard" for police funding
- 'Palpable anger' among police officers over pay
- Chief Constable Simon Byrne warns low pay could see PSNI losing officers
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