Nurses should not be working in managed isolation and quarantine facilities as well as hospitals and aged care facilities, the Nurses Society says.
The Nurses Society represents more than 5000 nurses, of whom more than 100 are known to be working in managed isolation and quarantine hotels.
Director David Willis told Nine to Noon the society has urged its members not to work across different locations, because of the risk of spreading Covid-19.
He said the society had raised its concerns with district health boards.
He said the prohibition on working for more than one employer was relaxed at the time the country moved to alert level 1, but his union believed it should still apply for those working in managed isolation, quarantine and border roles.
"It's really being super-cautious - it's the belt and braces approach ... we don't want any weak points."
Geneva Healthcare currently holds the nursing services for the 32 isolation and quarantine facilities across five different regions.
Willis said nurses are being advised to tell their DHB if they are working in a quarantine facility one day and then switching to a hospital in the following days.
In some cases hospital management would be unaware it was happening, in other cases nurses had been told it was acceptable as long as they weren't working excessive hours.
In the managed isolation facilities they were doing daily health assessments of people and dealing with any health problems they may have.
However, some are working in quarantine facilities where there are active Covid-19 cases and also in emergency departments in hospitals.
"Our view is that ideally these facilities should have dedicated staff but at the very least the DHBs and other health services should know when someone is also working in a managed isolation facility and a quarantine facility and at the moment they don't."
It was doubly important because another assessment could be made on whether it was prudent for the person to be working at different workplaces and also it would provide some employment protection for the nurse if a problem arises.
Willis said although Geneva handled bookings for nursing shifts at the isolation facilities, the DHBs will take over this work from next month.
Once the DHBs took over the hiring he believed some of the practices would be tightened up.
He said the need for nurses in the managed isolation facilities would continue for some time so it would definitely be sensible and preferable to have a dedicated workforce to avoid the risk of cross-infection.
Kate Weston of the Nurses Organisation - which represents 50,000 nurses - said there is a limited pool of nurses who can do the work.
It was not realistic to have a dedicated workforce in the managed isolation and quarantine facilities, she said.
"Those who have tested positive [for Covid-19] have not required hospitalisation and there have not been any situations where there has been a community spread because of a worker..."
She said it was only a small number of people who were working in more than one workplace.
Auckland's three district health boards have protocols in place to allow some nurses to work for both hospitals and managed isolation and quarantine hotels.
In a statement, the Waitematā, Auckland, and Counties Manukau DHBs say they follow regional guidelines to allow nurses to move between patients with Covid-19 and non-infectious patients in different workplaces.
They say there have been no known instances in Auckland of a DHB worker infecting a patient during the pandemic in hospitals.
In a statement Health Minister Chris Hipkins said he is always looking for improvements to the system and he is seeking further advice on nurses working in more than one workplace.