Fianna Fáil leader Micheál Martin has said that he has documents which suggest Gardaí failed to act on allegations of murder and other serious crimes.
Deputy Martin says he has handed the documents to the Department of the Taoiseach for full investigation.
They were obtained from Sergeant Maurice McCabe, the Garda who has raised concerns about the management of the penalty points system.
Deputy Martin says the whistleblower's claims need urgent consideration.
"I have sent material now to the Taoiseach in relation to other issues that the whistleblower has raised, which relates to the failure to fulfil basic functions in a range of cases - very, very serious cases involving abduction, assault, and ultimately murder - which leaves huge questions for response," he said.