Junior doctors are rejecting claims by District Health Boards that they are making up stories about how dangerously tired they are.
The doctors are going to go on strike for 48 hours in a fortnight over a roster dispute with the DHBs.
The Resident Doctors Association has previously said junior doctors may be required to work seven consecutive 10-hour night shifts, or 12 consecutive day shifts of up to 16 hours, with just two days off before returning to work.
And junior doctors have recalled falling sleeping while driving and giving patients the wrong medication because of fatigue.
But DHBs say they have not been able to verify any of the claims made in the union survey backing up how tired the doctors are.
On Tuesday, a spokesperson for the DHBs, Julie Patterson, said they had not been given access to the survey.
But the Resident Doctors' Association's national secretary Deborah Powell said the DHBs were given the 20-page survey report two months ago.
"The District Health Boards have found themselves in a corner over this one and they're coming up with all sorts of stuff to try and defend what is an indefensible decision, to be entirely honest," she said.
She even offered them the chance to peer-review the raw data, which the health boards refused, Dr Powell said.
"There's a deal to be done here, but the more that they attack the [junior doctors], the more that they defend the indefensible, the more difficult it's going to get," she said.
RNZ contacted the DHBs for comment and has not yet received a response.
Senior doctors urged not to strike-break
Senior doctors are being urged not to strike-break or do anything that would undermine junior doctors' industrial action.
Ian Powell from the Association of Salaried Medical Specialists, said he was telling members to stick to their own jobs unless a patient's life was at risk.
"If they're seen to be strike-breaking, that's an incentive for the DHBs to take a more hard-line position in the negotiations and that will prolong the dispute.
"It would be devastating for workplace morale as well amongst the medical profession."
Relationships between doctors and district health boards would remain poor until the health sector was properly funded, he said.