An investigation of a complaint about how the PSNI handled reports of alleged child abuse has found police there failed those who were said to have been abused.

The investigation, by the Police Ombudsman's Office in Northern Ireland, also found that the PSNI's predecessor - the RUC - had information about the alleged abuse 10 years earlier but did not investigate it.

In 2010 Mairia Cahill, who is a member of a prominent Republican family, told police she had been sexually abused by a prominent IRA member from 1997 to 1998, and in subsequent years was subjected to an IRA 'investigation' of her allegations.

Two other women also said they too had been abused as children by this man.

The PSNI began investigations into both these matters, which resulted in a number of people being prosecuted.

In 2014, the trials of the man accused of the rape and of those accused of involvement in the IRA investigation collapsed when Ms Cahill and the two other women withdrew their evidence, citing a loss of confidence in how the matter had been dealt with.

Mairia Cahill, looking over Dublin city, made a complaint of sexual abuse | Image: Sam Boal/Rollingnews.ie

In 2015, a review by Keir Starmer found the North's Public Prosecution Service had failed the women.

Ms Cahill also made a series of complaints to the Police Ombudsman's Office about the PSNI's handling of her report to them.

Police Ombudsman Dr Michael Maguire has met her to discuss his investigation's findings.

Overall, the Ombudsman found that the PSNI investigation had failed the victims.

But he did not support the allegations that it chose not to arrest some of the individuals concerned because they were police informants and that it had been subject to political interference.

Dr Maguire concluded that as a victim of crime, Ms Cahill had been failed by police in a number of key areas.

He was critical of the decision not to hold a serious case review and the circumstances of the police decision to split its investigation across two units: one which specialised in dealing with victims of sexual assault and one with experience in dealing with terrorist issues.

He said: "I accept that police wanted to move quickly on the sexual allegations and to use their different expertise to maximum effect.

"While I do not agree that this led to evidence being diluted, it did bring about a disjointed approach by police in their investigations and their treatment of Ms Cahill.

"There is no evidence they considered any other approach, such as creating a team with the range of skills to investigate these matters as one case," he said.

"Inconsistent approach"

The Police Ombudsman found that the PSNI had "an inconsistent approach" in its investigation of some of the people suspected of IRA membership - which in one case led to an individual not being arrested and questioned.

He found no evidence, however, that anyone had been protected from prosecution.

Dr Maguire did not find evidence to support the allegation that the PSNI investigation became subject to adverse political interference.

He added: "There is no doubt that this case was among those which caused considerable discussion among republicans and their political representatives.

"Despite this, we have found no evidence of adverse political influence on the investigation".

The investigation also did not support the suggestion that police inaction was such that Ms Cahill had to direct how the investigation progressed, but said its lack of a strategy for researching information already in the public domain contributed to her mounting concerns.

The Police Ombudsman recommended that four police officers be disciplined.

Three have now been disciplined - while the fourth had retired.

Dr Maguire also made recommendations for changes to seven PSNI policies.