New data from Te Whatu Ora shows 36 percent of Middlemore Hospital emergency department patients waited more than six hours to be seen in December.
The target is for 95 percent of patients to be seen in less than six hours. The latest ED wait time statistics have been released after criticism over the accuracy of previous metrics.
The only regions that fared worse in December were Wellington's Capital & Coast, where 47 percent of ED patients had to wait more than six hours, and MidCentral at 52 percent.
National Party health spokesperson Dr Shane Reti said the figures only included patients who had been admitted, transferred or discharged.
It means patients who leave before being triaged and/or admitted, such as the patient at Middlemore last year who died, would not show up in the numbers.
"There are patients at Middlemore who will leave because they don't want to wait. But within 24 hours, many of them will be back in ED."
The problem was tragically illustrated with a patient's death in June last year, Reti said.
The woman first arrived at Middlemore Hospital emergency department about 1am with a severe headache and was told it would likely be hours before she could be seen. She left.
She then returned in an ambulance a few hours later after a "massive" brain haemorrhage and died the following day.
Former Te Whatu Ora - Health New Zealand chairperson Rob Campbell said last month that workforce shortages plaguing Middlemore's ED would not be addressed in time for the winter flu season.
His remarks followed comments from frontline healthcare workers who said the hospital's ED was haemorrhaging staff and they were concerned about the impact on the department's ability to function during winter.
In a statement, Te Whatu Ora - Health New Zealand chief executive Margie Apa said:
"We acknowledge that, in many areas, the performance metrics are showing a decline, which means people are waiting longer to be seen in our emergency departments," she said.
"The causes of these delays are well documented, with the complexity and acuity of care required and workforce shortages of greatest concern.
"Our focus remains on fixing these issues and we are working right across the sector looking at immediate and longer term solutions. This will take time and consistent effort."
Minister of Health Ayesha Verrall was approached for comment.
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