Recently introduced hospital rosters increase the risk of harm to patients and reduce vital opportunities for training, a rebel group of junior doctors warns.
Fifty trainee surgeons have formed a new union called Specialty Trainees of New Zealand, or SToNZ, and the group has initiated bargaining with all 20 district health boards for a multi-employer collective agreement.
The move has angered the main junior doctors' union, the Resident Doctors Association, which said the trainees weren't association members, don't want to work safer rosters and could have rejected the pay deal.
Resident Doctors Association members went on strike twice in 2016 and 2017 to protest long working hours, which they said also put patients at risk.
They struck a deal with DHBs in March last year for better rosters, which meant they would not be required to work more than 10 days in a row, or four days straight.
SToNZ chair Heath Lash, a trainee orthopedic surgeon, said it meant that when they worked weekends they must take two consecutive week days off following the weekend.
He said he worked 13 weekends a year, which meant he misses 26 days of operating and elective surgery lists a year - times when he should be closely involved and learning.
"I want to be trained and to be trained I need to be in the hospital Monday to Friday because that's when the operations are happening, that's when the ... elective lists and elective clinics are happening that teach me how to do my job and be a good surgeon."
He also said being required to have days off during the week meant "you have to have really complex and complicated handovers. And so for a majority of specialties, the registrars or the trainees, they're actually the day-to-day point of contact person who runs the team and sees the patients almost every day.
"If you take them out of the hospital during the week, you have to have a lot of handovers, and we know that with handovers come mistakes. And with mistakes come big problems for patients."
Dr Lash also said the new rosters had led to a shortage of between 200 and 300 junior doctors.
Resident Doctors Association general secretary Deborah Powell rejected the claims.
"Putting it bluntly, they don't want to work safer rosters.
"And the RDA obviously is in support of safer rosters so that's what it has come down to. And they're interested in continuing to work the long, fatiguing hours that we stood against at bargaining last year."
Dr Powell said the RDA had investigated the claim about reduced training with the Royal Australasian College of Surgeons.
"They could see no threat to training and quite frankly we haven't either."
On whether there was an increased risk to patients she said: "That's totally untrue."