Gardaí made up 1.5 million fake breath tests between 2009 and 2016.
An investigation has discovered an extra 500,000 false tests and found some gardaí were exaggerating figures by 300%.
This internal report finds that almost 3.5 million breath tests were recorded on the Garda PULSE system, but just 2 million Drager breath tests were used.
Among the recommendations are that alcohol checkpoints are reduced, and that only positive breath tests are recorded.
Another report has looked into the issue of wrongful convictions when a fixed penalty should have been issued instead.
There were 14,700 cases where people were incorrectly penalised, and they're being appealed through the courts.
The internal reports have now been published on the Garda website.
File photo
Garda Commissioner Noirín O'Sullivan has said the failures highlighted in the reports are "completely unacceptable and all of us in An Garda Síochána must now take responsibility for ensuring this cannot happen again".
The Justice Minister says the reports identify serious and concerning problems within alcohol testing checkpoints and the fixed charged notice system.
In a statement, Charlie Flanagan said it's critically important that sanctions are applied where appropriate.
He added that he will take 'all appropriate action' when he receives a Policing Authority report on the revelations.
Opposition TDs, meanwhile, have called for the resignation of Commissioner O'Sullivan in the wake of the reports.
Sinn Féin justice spokesperson Donnchadh Ó Laoghaire says they need to examine the future of the Commissioner.
"It raises serious questions, yet again, about the culture within the senior levels of An Garda Síochána - there seems to be a culture of impunity.
"Nobody has been held accountable for this, that's simply not acceptable.
"I think it raises, again, further questions about Garda Commissioner Noirin O'Sullivan - who I would reiterate needs to go".
Tánaiste @FitzgeraldFrncs says news of Gardaí making up 1.5m breath tests is 'deeply disturbing' pic.twitter.com/rkBqqb6OwP
— Sean Defoe (@SeanDefoe) September 6, 2017
