"There were significant deficiencies in the police investigations, in particular the steps that police took as an employer to establish whether their staff may have engaged in misconduct."
While attempts were made to resolve the employment concerns by an "alternate resolution pathway".
"However, the process became unduly complex which hindered the final actions that could be taken by the employer," IPCA said.
Police also tried a restorative approach but, the purpose was "not clearly defined".
The complaint also raised potential criminal conduct by both staffs. However, the investigation found insufficient evidence to lay criminal charges.
The investigation found that roles and reporting lines were not properly followed alongside "significant procedural issues".
An internal review of the investigations was completed by police following concerns from the IPCA.
"The authority agrees with the findings and recommendations of that review, which largely confirm the authority's independent view."
The IPCA which was established by Parliament in 1989, investigates and resolves complaints laid against police.
Once it receives a complaint, the IPCA may carry out an investigation, refer the complaint to the Police for investigation or coordinate the resolution of the complaint.
