Whangārei Hospital nurses asked bosses to bring in the army to help with extreme understaffing at the height of the flu season last year.

Emergency department (ED) nurses issued a formal health and safety complaint to the hospital in September that has just been released under the Official Information Act.

The complaint said urgent help was needed because the department was so understaffed it was "extremely unsafe".

It asked the hospital to employ army medics to cover shifts - one of a series of measures suggested to help.

There were 240 roster gaps in a four-week period, not counting sick leave.

"The physical and mental load on the staff trying to cover the roster gaps is immense," the complaint report said.

The department was made more dangerous because the fill-in nurses were often inexperienced and untrained in emergency work, it said.

Association of Salaried Medical Specialists executive director Sarah Dalton said the complaint showed the depth of stress staff were working under.

"What do you do when there is a crisis? You call in the army," Dalton said.

The nurses also asked for elective surgery to be stopped for three weeks and for outpatient clinics to be called off if needed so staff could be redeployed to help in the ED.

It asked bosses to lobby to sort the visa status of existing staff, fearing they might have to leave, and to start a worldwide recruitment drive.

Te Whatu Ora did not treat the formal complaint as valid, because the person who issued it did not have the full health and safety training required and did not consult with management first, as required.

Despite that, the hospital said it was taking the concerns raised seriously.

The interim district director, Tracey Schiebli, said they were working with the team to improve recruitment, and to move staff to the ED when there were spikes in demand.

"However, overall progress is slower than we would have liked as we grapple with continued attrition of senior experienced nursing staff and gaps resulting from long-term leave," Schiebli said in a statement.

Any decision to deploy army medics would be made at a national level and would have a high threshold as a national emergency response, she said.

Dalton said doctors on the ground told her the pressures now were just as bad as in September.

There were still huge nursing shortages, there were not enough junior doctors on at night, and there was a paper-based system for some services like radiology, she said.

"Every day is a difficult day at Whangārei Hospital," she said.

RNZ understands the nurse who issued the notice has since undertaken the required health and safety training.