Fitzgerald was told about claims of misconduct in the force two years ago
Allegations by two gardaí that management failed to warn them about a threat to their safety from an 'off the books' informant were first brought to Tánaiste Frances Fitzgerald's attention two years ago.
The two gardaí claim that the informant - a suspect in the case of missing man Patrick Heeran - was protected by other gardaí.
They claim that their homes were monitored by a gang who were prepared to attack them in 2009 and that the gang leader was later a suspect in Mr Heeran's 2011 disappearance.
They say he should have been arrested, rather than being overlooked by officers.
The two gardaí are understood to have raised the allegations with Garda authorities as far back as 2011 - and one of their wives also complained to the Garda watchdog GSOC.
The officers later raised their concerns with former Fine Gael MEP Jim Higgins, who passed on the information to the then justice minister Alan Shatter in April 2014.
Mr Higgins also provided a dossier on the case to Ms Fitzgerald when she took over from Mr Shatter in May 2014.
The matter was raised by Sinn Féin TD Martin Kenny in the Dáil on Thursday as part of a series of allegations of Garda malpractice in Leitrim. He said he had "serious concerns" about the investigation into the disappearance of Mr Heeran.
Last night, Mr Kenny said that the two officers approached him after becoming "frustrated" by the alleged "inaction of the authorities". He said they received a letter in November 2015 telling them that the Independent Review Mechanism at the Department of Justice acknowledged their concerns but would "not be carrying out any further investigation".
Last night, the Irish Independent asked the Justice Department what actions Ms Fitzgerald had taken since receiving the information about the two gardaí's claims in 2014.
A spokesman said: "It is difficult to respond definitively, given the incompleteness of information in the public domain.
"However, some of the details mirror a case which was referred by the Tánaiste to the Independent Review Mechanism, where the complainant was informed of the outcome."
He said that he couldn't comment on the outcome of the case as it is "confidential to the complainant".
The spokesman said it was open to Martin Kenny or anyone with information on the matter to complain to GSOC.
A GSOC spokeswoman said the agency "listened with concern" to the matters Mr Kenny raised in the Dáil.
"A small number of the cases listed by Deputy Kenny have either already been investigated by GSOC or are currently under investigation."
The spokeswoman would not comment on specific cases and said officials from the agency would meet Mr Kenny next week.