Former Northern Ireland police ombudsman Nuala O'Loan has told RTÉ that trust between An Garda Síochána and the Irish people "has been seriously undermined" as a result of recent controversies.

Ms O'Loan told RTÉ's This Week programme that a commission of inquiry, staffed by international experts and with powers to access garda documents, would be required to restore trust in policing.

"I think a national commission of inquiry is required now, and possibly an international commission of inquiry, that would send a very clear message about the intentions of Government,” she said.

"I think if such commission were appointed, it would need to have people from outside the island of Ireland serving on it."

Ms O’Loan described the recent revelations about the near 100% over-reporting of breathalyser statistics as "mind-boggling", and questioned how the thousands of hours associated with conducting such tests might have been factored into the budget for An Garda Síochána.

She said the recent revelations on inappropriate fixed-charge notice convictions, financial irregularity in the Garda Training College and media reports on investigations into homicide statistics raised serious questions about the basis for planning and funding An Garda Síochána.

"The whole planning and funding of the guards is predicated on the work that they do and it seems unlikely to me that erroneous statistics are going to be limited to these three or four areas," she said.

Asked if she believed GSOC should investigate if any overtime was claimed for conducting the over-reported breath tests, Ms O'Loan said "You'd have to look at the individual facts of each case, but that would certainly suggest to me a criminal inquiry. Certainly in the event of evidence of criminality, you are looking at something that is very serious and independent, in terms of an inquiry into the guards".

She was also critical of the speed with which An Garda Síochána had reacted to concerns raised by whistleblowers.

"I can't help noticing, because it's quite unusual, the number of whistleblowers who've come forward to raise concerns about the guards. And then you look at the way in which it's treated. And you look at the time that elapses before anything is either done or not done and I think there's a cultural issue around how you actually deal with it," she said.

She was also critical of the pace of the gardaí in dealing with the fixed-charge notice and breathalyser issues.

"They should have moved much faster. As soon as they became aware of it. As soon as you realise that your police force is putting people before the courts who shouldn't be there, there should be immediate action,” she said.

“You should be talking to the courts immediately, starting to write the letters, starting to alert people that this has been wrongly done".

Ms O'Loan said it would not be appropriate for her to comment on whether the current Garda Commissioner Nóirín O'Sullivan should step down, but said that the findings of an internationally staffed commission would inform such decisions: "I think that if you started with a commission, what will need to happen, in terms of the current senior management will evolve as more inquiries take place and more questions are asked. I don't think it would be appropriate for me to comment at all".

She also said that any programme of policing reform should involve strengthening the powers of garda oversight bodies like GSOC and the Policing Authority.

Furthermore, she said: "I would suspect there are reforms needed in the Department of Justice because I think if we just look at what has happened to the Gardaí over the last few years, there have been clear, consistent indications that things are not as they should be.

“The role of the Department of Justice and the closeness between the Department of Justice and the Garda Commissioner and senior garda management doesn't seem to have produced the level of robust management that's needed.

“So my suspicion is you would have to look at the role of the Department of Justice."

Ms O'Loan served as Northern Ireland Police Ombudsman from 1999-2007, during the reforms recommended by the Patten Commission being implemented, which saw the transition of the RUC into the PSNI.