Emergency department wait times are now the longest in at least a decade as more than one in five people experience a treatment delay of at least six hours, the National Party claims.
Those on the frontline also admit triage times and standards of care are slipping.
Health spokesman Dr Shane Reti cited data obtained by the Parliamentary Library, which he said showed since 2017 there has been a "marked decline" in the number of people seen within six hours at an ED.
"In the three months to the end of March, the proportion of people admitted, discharged or transferred from the emergency department within six hours of arriving fell to 78.5 per cent, the lowest in more than a decade," Reti said.
"It was the second quarter in a row that more than one in five people going to the Emergency Department has had to wait at least six hours for treatment, a sure sign that the system is not coping."
The latest data sourced by the Herald, for May 2022, shows the average wait time at an ED nationally was 287 minutes (a little under five hours), compared to 270 minutes in May 2021.
Te Whatu Ora – Health New Zealand said it is working "as quickly as possible" to implement changes and provide relief to a besieged health system, including expanding telehealth, which are consultations with a health practitioner via communication technology.
Reti said when ED waiting times are unbearable, people simply leave – sometimes with tragic consequences.
Reti also spoke of the situation at North Shore Hospital where an elderly woman was treated in a leaky and draughty triage tent, which was first reported by the Herald.
"When did tents become emergency departments? When did we say leaky tents [were] okay to triage or observe patients who were so urgent they were turning up at emergency departments? It's never okay," Reti told NZME.
National would use funds designated for what Reti said were bureaucratic health system reforms to help build the medical care workforce and also alter immigration settings to increase the attractiveness for offshore workers, specifically nurses.
"Exhausted, hard working ED staff see no support, hope, or plans in Andrew Little's public statements," Reti said. "The Minister of Health urgently needs to refocus the $486 million being spent on health reforms towards relieving pressure in EDs."
Little did not reply to questions sent to his office by NZME about Reti's claims.
Last week, however, he told RNZ it was a "really tough winter" and the Government was working to fill staffing gaps.
"We have a chronic staffing shortage and we are having one of the worst winters we have ever had because of Covid ... because of the flu season we are having at the moment.
"In terms of the long-standing staff shortages, the work is ongoing to fill those gaps. Nothing stops in that respect - that work continues."
New Zealand Nurses Organisation president Anne Daniels, who works some evenings and weekends in EDs, agreed wait times are growing.
"We're failing now," she told NZME. "We can't do it anymore, we haven't got the resource to make our triage times and our standards of care where they should be.
"We've been failing for a long time but we've been plugging the gaps."
She said successive governments have "turned their back" and ignored the realities of the health system.
Daniels also said a looming issue with the potential to compound the crisis was veteran nurses approaching the age of retirement.
The country's 20 former district health boards warned the Government last year of "critical workforce issues" with some overloaded hospitals at "code red".
Replying to the Herald's questions, a spokesperson for Te Whatu Ora – Health New Zealand said the country's new national authority is "closely monitoring" the pressures across our health care system.
Omicron, new Covid-19 subvariants, flu and other respiratory illnesses have all had an impact, they said.
"We know services are finding this winter challenging and we are working with regions and districts to implement a range of initiatives."
Te Whatu Ora said hospitals are co-ordinating planning to ensure resources are deployed and shared to support access to care where it is needed.
"We're also making it easier for GPs, ambulance services and Healthline to make direct referrals to radiology, reducing the need for ED admissions," the spokesperson said.
If capacity permits, GP opening hours for urgent care are also being extended into evenings and weekends.
"We want to acknowledge the ongoing hard work of our healthcare teams - the work they do is important and valued," the spokesperson said.
"Our healthcare teams are part of the community, too, which means they are also vulnerable to Covid-19 and winter illnesses and this has an impact, with some staff absences. We have confidence in all those frontline professionals who are dealing with these challenging conditions."
During the past two weeks, there has been a significant increase in Covid-19 cases, on top of other respiratory illnesses.
"While this isn't unexpected in winter, we are seeing its impact earlier than usual with more cases presenting to our emergency departments, general practices, and medical centres," the Te Whatu Ora spokesperson said.
Over the past two months, they added, some EDs have been experiencing higher presentation volumes of between 21,000 and 23,000 presentations per week.
However, this rate of ED presentations nationally is in line with rates seen in recent years.
Te Whatu Ora assured the public if people if they need urgent hospital-level care, they will receive it.
"Our best protection this winter is to be up to date with influenza and Covid-19 vaccinations, which can help reduce the need for hospitalisation, along with the other precautions of staying home when sick; getting tested when you have flu-like symptoms; wearing masks as directed; and regularly washing hands," the spokesperson said.