Nurses have lost a legal fight over claims of staffing shortfalls at public hospitals, with a judge throwing out a union bid to have the NSW government hit with penalties for understaffing. 

The NSW Nurses and Midwives' Association launched the Supreme Court action against the government in March 2023, accusing it of repeatedly breaching award conditions.

The union argued nurse-to-patient ratios - the minimum number of nurses required to care for patients - were frequently below the figure set under employment awards in place from 2018 to 2021.

It claimed the government breached the awards by failing to meet the required ratio of six nursing hours per patient day, and pushed for it to be hit with civil penalties.

Worker numbers fell short in more than 1400 week-long periods when considering the actual number of patients and staff hours worked per week, the union claimed.

However, Judge David Davies on Thursday found the government did not breach the award after it argued it was only required to roster nurses in accordance with the nurse-to-patient ratios.

The ratios could then be subjected to a "spot check" at a nurse's written request to confirm whether they were actually met.

If shortfalls were identified, action was taken after the fact.

"The defendant submitted that the textual framework of the award supports the conclusion that ... (it) only requires that the defendant rosters nurses in accordance with the specified (nursing hours per patient day) based on historical patient numbers and then takes rectification action if required on a spot check," Justice Davies said in a judgment on Thursday.

"(The government argued) there is no express requirement ... in the award that the specified ((nursing hours per patient day) must actually be provided at the conclusion of a week.

"If that was intended it would have been straightforward for the requirement to be set out in that way."

The judge ultimately agreed with the government, saying the award pointed strongly to the conclusion it sought to achieve reasonable workloads through proper rostering along with the spot checking system.

He found the government did not breach the award, dismissed the case, and said he would decide the issue of court costs at a later date.

"In my opinion, the defendant's position is the correct one," Justice Davies said.

The hospitals where the union alleged understaffing happened were Gosford, Wollongong, Royal North Shore, Prince of Wales, Concord, Royal Prince Alfred, Liverpool, Bankstown/Lidcombe, Nepean and Westmead.

The court case was filed when the then-Liberal government was in power under premier Dominic Perrottet.

Labor premier Chris Minns later took power and introduced a minimum staff ratio of one nurse for every three patients in emergency rooms.