The number of riot police in the region has almost halved since 2000 following the decision of the IRA and loyalists to decommission weapons.
However, heightened tensions surrounding loyal order parades and Union flag protests means public order police units have an increased workload, Criminal Justice Northern Ireland found.
The report stated: "In the absence of an overall comprehensive strategic threat and risk assessment, it is impossible to say whether the reductions in TSGs (Tactical Support Groups or riot police) were entirely justified.
"It may well be that they were justified or indeed inevitable in the circumstances, given the significant pressures to reform and achieve efficiencies and normalisation.
"But the envisaged peaceful situation which was referred to by the Independent Commission on
Policing in 1999 does not reflect the current policing environment."
Financial pressures and the abolition of the full-time reserves has contributed to a reduction in the number of tactical support groups and part-time public order units that support dedicated riot police.
The report also highlighted an ageing workforce and injuries or restrictions on duty.
The independent review stated: "Inspectors also heard clear evidence of some disquiet that the public order capacity had been stretched in recent years.
"Various interviewees expressed the view that requests for public order support were often reduced to meet the available resource, rather than meeting the operational requirements.
"Senior officers also acknowledged the fact that some parts of the organisation were 'fatigued' by recent deployments and events."
The report found although it is inevitable that public order capacity would be stretched at times, having an underused department was not the solution, as lack of deployment would make it less effective.
"The key issue seems to be one of a reasoned analysis of the future need with the objective of creating the greatest amount of flexibility possible," it added.