The serving officers are also taking fair employment tribunal proceedings against Chief Constable Jon Boutcher and his deputy, Bobby Singleton.
The Policing Board has also been asked by the officers to appoint an independent external body to investigate.
The three officers were formerly members of the PSNI’s Close Protection Unit (CPU), which provides security services to high-profile figures, often referred to as ‘principals’.
It is understood the highly trained unit is now the subject of an internal PSNI investigation.
In addition to providing cover for senior politicians, legal and other figures, the CPU is regularly tasked with protecting visiting dignitaries, including members of the British royal family and US presidents, including Joe Biden in 2023.
It is understood that the three Catholic officers allege they were ‘repositioned’ to administrative roles earlier this year after raising concerns about several issues, including sectarian abuse and discrimination in the workplace.
The Irish News further understands that two of the three officers are now the focus of criminal investigations launched after they raised their original concerns, while a third is the subject of an internal PSNI probe.
It is understood the officers initially made a number of ‘protected disclosures’ that set out a range of serious concerns.
In addition to alleged sectarianism, it is believed the three officers also make claims on health and safety issues and misuse of public funds.
It is believed other officers attached to the CPU, who initially made complaints, have since left the police.
It is understood that after complaints were made, the PSNI carried out an internal review focused on the CPU.
After the internal review was completed, two of the officers were cautioned by the PSNI’s Professional Standards Department (PSD) over allegations of harassment, and it is understood the pair are set to face formal criminal interview in relation to this.
It is believed the alleged harassment allegations arise from communications with line managers about the protected disclosures.
A third officer is facing an internal misconduct investigation, which again is linked to communications with management. It’s understood the officer was representing the Police Federation.
A spokesman for KRW Law said his firm is “representing several members of the Police Service of Northern Ireland Close Target Protection Unit on legal issues pertaining to work practices within the workplace.
“No further comment is offered at this point in order to protect ongoing legal procedures and processes and to protect the integrity of evidence.”
The Catholic officers’ legal team has written to senior members of the Policing Board setting out their concerns. The Policing Board forwarded the correspondence to the Police Ombudsman.
The three officers have now asked the Policing Board to appoint an independent external body, unconnected to them or the PSNI, to investigate their allegations.
The Policing Board was asked what action has been taken in response to the correspondence from the three officers and if it was distributed to board members.
The board did not respond to either question.
“The board will not be offering any commentary on correspondence deemed confidential to the Board,” it said in a statement.”
The Irish News also contacted the Police Ombudsman’s office, which refused to say if it is investigating the allegations raised in the correspondence.
“Any correspondence received by the Police Ombudsman from the Policing Board is in confidence and it would not be appropriate for this office to comment,” a spokeswoman said.
A spokesperson for the PSNI said: “As there are ongoing criminal and misconduct investigations as well as industrial tribunal proceedings it would be inappropriate to comment.”