An anaesthetist at North Shore Hospital, Julian Fuller, said he regularly saw the impact.
"Only a few months ago I saw a little old lady who'd been forced to walk around on crutches for over a year waiting for a hip replacement and that's completely unacceptable," he said.
It was frustrating and having a big impact on people's health, he said.
"We see a number of people who are presenting who should have presented six months before or three months before and are now often more seriously ill than they were before. That's presenting a more serious risk for anaesthesia and that's not good medicine," he said.
The union said a number of specialists in the public system were facing burnout.
Executive director Sarah Dalton said they had little time between patients to train or to take stock of their work.
"That is a massive concern to us, particularly when we see that it is an ageing workforce," she said.
Dr Fuller said more money needed to be spent if New Zealand was going to have a first-rate health system.
"At the moment we're spending sufficient money for a second-rate health system, where access to a lot of expensive drugs is not there and access for treatment of simple diseases is not there," he said.
Consideration should be given to increasing the size of the medical schools, he said.
The report found fewer new graduates were going in to specialist training and that could mean there would not be enough doctors to replace the current workforce, which had an average age of about 50.
Dalton said specialists took at least 12 years to train, so action needed to be taken now.
Part of the problem was that existing senior doctors were too busy to train new ones.
The survey also showed the country relied heavily on overseas-trained doctors, but there was uncertainty about how many could come due to Covid-19.
