The National Party is calling for clarity as 1600 jobs at Te Whatu Ora Health New Zealand go up for consultation.
More than 80,000 people work for the mega health authority since the 20 former district health boards were merged into one centralised system last July.
The large-scale health reforms introduced nine months ago were expected to address the job duplications caused by the merger.
In a statement, Te Whatu Ora said 1600 jobs will be affected, and include roles from executive leaders through to those working in commissioning, finance, and service improvement and innovation.
While Te Whatu Ora said front line staff will not be impacted, some in primary care are concerned it may add to their already heavy workload.
"It's at an admin level that it's going to hit the individual practices and probably slow down a number of the processes that we have to go through with them," Iain Watkins of West End Medical Centre said.
National is demanding to know what it will mean for a health system already under stress.
"What we understand is they're back-office jobs but if they're jobs like payroll, good luck with messing with people's pay," the party’s health spokesperson Dr Shane Reti said.
"I think [Health Minister Ayesha Verrall] needs to clarify which jobs, exactly which hospitals and how many."
Te Whatu Ora declined 1News' request for an interview, saying no decisions have been made at this stage. It added that the process is around impacted roles, which does not necessarily mean job losses.
In a statement, Verrall said: "As part of the health reforms, we knew there would need to be efficiencies made."
Reti said while he understood why efficiencies have to be made, he questioned the timing of the move.
"Why are we are we shuffling the deck chairs in the middle of a pandemic and when we've got emergency department times the worst we've ever seen and surgical wait times the worst they've ever been?"
Decisions around staffing will be finalised in early June.