Terry Spence, who chairs the body representing rank and file officers in Northern Ireland, has been campaigning for additional police resources.
He says over 350 officers have been injured as a result of public disorder from loyalist and republican crowds in the last eight months.
Mr Spence says "normal policing" has been suffering as a result of the physical and financial strain.
"This is the most challenging period for the Police Service of Northern Ireland since its inception in 2001 and it's very clear that that situation will continue to deteriorate if we do not have the additional resources that we have called for," he told UTV Live Tonight.
"It's apparent that because of the very severe threat from dissident republicans, coupled with the very serious public disorder which is being orchestrated by loyalist paramilitaries that the police service are being distracted from delivering normal policing in Northern Ireland," he added.
It comes after PSNI Chief Constable Matt Baggott publicly admitted to needing more officers for the first time last week.
The Chief Constable hinted at a new recruitment campaign when he addressed the Northern Ireland Affairs Committee in Westminster.
Looking forward over the next two or three years, judging that against the way in which we've seen the last six months unfold, I think it's inevitable we will need to have more police officers.
Chief Constable Matt Baggott
Northern Ireland had a police force of more than 13,000 officers before the Patton reforms were implemented over a decade ago. The PSNI now employs 7,000 officers.
"At the minute the sums simply don't add up," UTV's Sharon O'Neill explained. "Police reforms didn't envisage that almost 15 years after the Good Friday Agreement there would still be so much unrest on our streets."
Privately, senior officers say policing the ongoing flag dispute is becoming unsustainable.
Security journalist Chris Ryder says "there is a sense of panic in headquarters".
"They see no end to this and (...) even if they see an increase in recruitment it'll be up to two years before those boots are on the ground," he added.
Major security operations have been mounted in Belfast to police the weekly loyalist protests held each Saturday at City Hall since December.
Meanwhile, dissident republicans have been blamed for two separate bomb attacks targeting police officers at their homes in Omagh and east Belfast in the past month.
Jim Gamble, who was a police officer for three decades during some of the worst years of the Troubles, says the PSNI needs to manage its frontline resources.
"We're talking about officers in the PSNI, who have a lot of experience in policing public order. Now I often hear people say: 'Well, they have lost all of the experience in the RUC' - and I think that is an absolute red herring."
"Whatever those additional numbers are, they'll be critical if the PSNI is going to have the ability to flex. We all thought we had come through the peace process and that we were heading (...) towards much more peaceful times.
"Now, we have to recognise that there will be bumps on the way and for the past number of years, we've experienced those during the marching season. Well, there are going to be other issues because of the insecurities in both communities that are going to require policing to face in multiple directions at the same time."
This summer alone, the PSNI will need to police the G8 summit in Enniskillen in June and the World Police and Fire Games in Belfast in August, along with the traditional marching season.