The internal Audit Committee of An Garda Síochána has said it was "very concerned" that senior garda management did not tell it about the existence of thousands of fake breath tests or unreliable fixed notice convictions.
The claims were made in the latest annual report from the Audit Committee and reported by RTÉ's This Week.
The committee, which oversees spending in the force, said it was kept totally in the dark over both issues despite senior management knowing about them in the previous year.
It said it was unable to publish the 2016 report by its March 2017 deadline due to two high-profile announcements by Garda management relating to both these matters, which were not notified to the audit service in advance.
The report says that neither the committee nor the Garda's internal audit unit had been informed, even though senior gardaí had already devoted considerable resources to examining both.
As a result, the committee said it has been "placed in the unusual position of being unable to offer any view concerning the implications of either issue".
In a statement released this evening, Minister for Justice Charlie Flanagan said: "I am aware that the issues referred to have been raised, and expect to be in receipt of the forthcoming internal AGS report into these issues, and also the report commissioned by the Policing Authority in the coming weeks.
"This will present a fuller picture of what has taken place. As there are a number of investigations currently ongoing, I do not believe that it would be appropriate to comment or potentially pre-empt their findings.
"I am aware that AGS is working to improve its communication with the present Audit Committee to ensure it's satisfied that it's informed of all relevant information."
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The committee has paid particular attention to the issue of Fixed Charge Notices (FCN) ever since problems were flagged with the penalty points system by Sergeant Maurice McCabe.
The report says that the committee had spent significant time examining the FCN system and were prepared to give it a clean bill of health, when senior management revealed that some 14,500 convictions relating to the system were unreliable.
Despite knowing about the problem since 2016, and knowing the the Audit Committee has kept a watching brief on the FCN system, senior Garda management had not told the committee about the issue.
The report says: "Prior to this public announcement and notwithstanding the very specific role assigned to the Garda Internal Audit Section in relation to FCN, neither the internal audit section nor the Audit Committee were aware that management had discovered a legal problem in the course of 2016 or that the organisation had devoted considerable resources towards ascertaining its scope and then devising and implementing a solution."
It says that the committee was "unable to offer any view concerning the cost implications of these events or the adequacy of the remedies that are being implemented".
As a result the committee said it must regard these issues as "unresolved" and that it has asked senior Garda management to be "examined thoroughly" on the matter.
The vice-chairman of the Public Accounts Committee said the audit committee report raised many questions.
Alan Kelly said there were cultural issues at the highest level in the force, and it was effectively preventing its own audit unit from doing its job.
"It's absolutely incredible stuff," he said.
"Obviously the relationship between the internal audit function and senior management in An Garda Síochána isn't functioning. The passing of information from one to the other isn't happening to the level required.
"Why weren't the audit committee told about this for over a year? How can they do their jobs? How can they actually assess risks and costs to the taxpayer if they are not provided information in the first place?" he asked.
Mr Kelly said the PAC was not provided with a copy of the audit committee's report despite asking for all relevant documentation on numerous occasions
He said the report raised serious concerns at the highest level, and he expected the PAC will return to the issue in the autumn as a result.