George Hamilton and a number of other senior Police Service of Northern Ireland officers are subject to the probe by the region’s Police Ombudsman. The PSNI said they “completely refute” all allegations.
The claims relate to how the force handled an inquiry into the awarding of a contract to supply vehicles to the force, in which Mark Gilmore, the former Chief Constable of West Yorkshire and a former PSNI officer, was among nine people interviewed.
At the conclusion of the 2014 investigation into bribery and misconduct in public office, no charges were ultimately brought against any of the men - all of whom denied any wrongdoing.
Mr Hamilton, current Deputy Chief Constable Drew Harris and current Assistant Chief Constable Mark Hamilton are all now being investigated by Ombudsman Dr Michael Maguire.
A number of other less senior officers are also under investigation. Dr Maguire has received complaints from a number of those investigated in the vehicle contracts probe in 2014, including Mr McCausland and Mr Gilmore.
It is understood the claims include allegations that police documents were altered.
Mark Gilmore was suspended on full pay by West Yorkshire’s Police and Crime Commissioner in June 2014 when news emerged of the investigation by PSNI into his relationship with a leading local car dealership.
Mr Gilmore, who had only been in post for 14 months at the time, was alleged to have been involved in an “inappropriate relationship” with senior officials from the firm since 2013 and used this relationship to “improperly promote” it within West Yorkshire Police and the region’s other forces.
He was also accused of using his professional relationship with the company to get a better deal when he bought the VW Golf, previously used for demonstration purposes, for his son Mark Gilmore Junior in 2014.
The Chief Constable, who insists he was wrongly accused and has done nothing wrong, had his suspension lifted in 2015 when Northern Irish prosecutors said he and eight others, including the owner of DMG, had no criminal case to answer.
But he never returned to his job and retired last August. He has since launched legal action against PSNI and, separately, West Yorkshire Police and Crime Commissioner Mark Burns-Williamson.
The PSNI issued a lengthy statement denying any wrongdoing. “PSNI can confirm that a number of senior officers, including the Chief Constable and Deputy Chief Constable, have been informed of complaints made against them by former senior PSNI officers,” said a spokeswoman.
“The complaints relate to allegations of misconduct by senior police during a criminal investigation by the PSNI into the two complainants, former senior colleagues, during 2014.
“PSNI acknowledges and supports the need for the Office of the Police Ombudsman to investigate these allegations and all officers are co-operating fully with the investigation.
“The Chief Constable, Deputy Chief Constable and other officers completely refute the allegations made against them and are strongly of the view that these complex investigations into the complainants were conducted with professionalism and integrity. This position has been fully outlined in the officers’ initial response to Oponi (Office of Police Ombudsman for Northern Ireland).
“Whilst ordinarily the Police Service would limit its responses on matters where it is under investigation, this case has particular and unusual aspects to it.
“This case has been the subject of recent speculative press and media coverage which has the potential to negatively impact on public confidence in policing.
“We have full confidence in the Oponi to complete a thorough investigation and we trust that they are left to do so without ongoing public commentary.”