Six government departments and six state agencies are in breach of laws aimed at protecting the Irish language, according to the annual report of An Coimisinéir Teanga.
The Department of Community, Rural and Gaeltacht Affairs is among the bodies failing to comply with the legislation.
Breaches have also been found at the National Heritage Council, the Equality Authority and the HSE.
The office of the Coimisinéir handled 600 new complaints last year, more than one-third of which came from Gaeltacht areas.
Almost two-fifths of the complaints came from Dublin, while 22% came from Galway.