An investigation has found that eight out of nine gardaí assigned to serve in the Donegal Gaeltacht could not carry out their duties through Irish.
The finding was contained in the 2011 annual report by An Coimisinéir Teanga, Seán Ó Cuirreáin.
It says garda management "failed to adequately serve native Irish speakers" in Gaoth Dobhair in the heart of the Donegal Gaeltacht.
The Garda Commissioner failed to comply with a provision of An Garda Síochána Act 2005, which requires that members of the force stationed in the Gaeltacht should be sufficiently competent in Irish to enable them to use it with ease in carrying out their duties.
The investigation arose from a complaint from a native Irish speaker who was unable to conduct his business through Irish with gardaí in Gaoth Dobhair.
The investigation, which began in February 2011, was temporarily set aside when garda authorities increased to three the number of Irish speakers assigned to the station.
However, the investigation was recommenced when no further progress was reported and a formal finding of non-compliance was made by An Coimisinéir Teanga in December 2011.
An Coimisinéir Teanga made a series of recommendations to be implemented by the Garda authorities within a nine-month period to ensure full compliance with the statutory requirements.
A statement from the Garda Press Office said the content of the report is noted by the Garda Commissioner and is receiving attention.