Five psychiatric nurses at the HSE's Áras Attracta facility in Co Mayo have been granted injunctions by the High Court, preventing the HSE from proceeding with an internal investigation into complaints against them.
Ms Justice Deirdre Murphy also ordered the HSE not to begin any further investigations unless they comply with its "trust in care" and disciplinary procedures.
The orders are likely to affect 12 other Áras Attracta staff subject to the same investigation.
The injunctions apply until the conclusion of the full legal challenge being taken by the five nurses, alleging the investigations breach their contractual rights.
Ms Justice Deirdre Murphy said the HSE had displayed a "reprehensible" attitude to the efforts of the nurses' trade union, the Psychiatric Nurses Association, to internally resolve serious issues about the conduct of the investigations.
Among these issues was the failure by the HSE to consult with the association about the make-up of the investigation team.
The judge said the nurses had made a strong case that the right to be consulted was of real substance and part of procedures that the HSE could not depart from at a whim.
She said the HSE had argued that the serious claims about the service provided at Áras Attracta had required it to move quickly.
But she said the court failed to understand why this required the HSE to depart from agreed procedures when there should be strict adherence to the procedures in precisely those circumstances.
The five nurses - Lyndsey Conway, Carmel Doherty, Mary Prendergast, Vidhya Maverly and Marie Kilcoyne - are among 17 Áras Attracta staff being investigated arising from complaints about matters featured in undercover filming by the RTE Investigations unit in 2014.
They will remain suspended on full pay pending the outcome of the legal proceedings. None of the five are subject to any criminal proceedings.
A spokesman for the HSE said it had not yet received Ms Justice Murphy's written judgement and that it would not be commenting on the case until it has considered it.
He said no decision on appealing the ruling would be made over the week-end.
