The National Party believes a growing number of mental health facilities could be in jeopardy because there are not enough workers to staff them.
It follows reports an extended care mental health unit within Christchurch's Hillmorton Hospital may close its doors as it has about half the workers needed.
Te Whatu Ora said the staffing situation for its inpatient extended care unit Tupuna was unsustainable.
National's mental health and suicide prevention spokesperson Matt Doocey said it was "hugely concerning" and suggested it was a sign of things to come.
Tupuna provides 24 hour care and support for people with mental health issues that require a longer stay in hospital than what its acute inpatient unit can provide.
Te Whatu Ora Waitaha Canterbury's specialist mental health services general manager Greg Hamilton said it is carrying a significant level of vacancies, "particularly within nursing".
"There is a national and international shortage of clinical specialists in mental health along with a national shortage of nursing staff across many regions and health specialities," he said.
"We continue to work proactively to ensure we can continue to provide safe care for patients and safe working environments for staff."
There is 9.25 full-time equivalent (FTE) nursing vacancies for the unit, which accounts for 48 percent, alongside gaps in clinical psychology and occupational therapy.
Te Whatu Ora said gaps are often filled by casual, pool and agency staff as well as staff from other areas.
A cutback from 15 to 10 available beds in the Tupuna unit happened last December with another bed removed in April.
"Despite the reduction in bed numbers, it continues to be difficult to cover all rostered shifts with the appropriate staff mix," Hamilton said.
"We are currently working through a change proposal with our staff."
It is proposed staff are relocated into either appropriate community placements or into another inpatient unit across the division.
Feedback on the consultation period was due this week and Te Whatu Ora plans to release the decision on Wednesday.
Doocey said it was concerning the government had no plan to respond.
"I think what we've got, there's a health minister, who's distracted on reforming the bureaucracy of the health system, spending hundreds of millions of dollars on health reform that's actually delivering worse outcomes," he said.
"And now we're learning that we've got a potential closure of much needed mental health beds in Canterbury.
"I think we're going to find that there'll be more closures around the country."
Data seen by RNZ showed more than 640 full-time vacancies in the mental health sector, for psychologists, psychiatrists and registered nurses at the end of June 2022.
Full-time psychologist vacancies across the country had grown by 140 percent in five years.
Doocey said the more existing mental health staff were stretched, the likelier they would burnout.
"When I talk to people with mental health, it becomes apparent pretty quickly, that the biggest obstacle for New Zealanders getting timely access to mental health care is lack of workforce.
"It's not good enough that we have large numbers of our mental health workforce who are leaving to other sectors because they're becoming work burnt out, covering many vacancies across our services."
In a statement, Health Minister Andrew Little acknowledged there were shortages across the health workforce, including in the mental health workforce.
He said there was investment committed into upgrades for Hillmorton's facilities.
"Recent consultation about proposed changes at Hillmorton is consistent with an apporach to manage patient needs to assist their recovery safely. Community placement is part of that when it is clnically deemed safe to do so.
The minister said vacancy data did not take into account private providers or other public setors like the Department of Corrections that employ their own mental health workforce including specialists.
"We started the green list which has opened the direct pathway to residency to all thirteen classes of nurses, when the previous system only enabled aged residential care nurses to do so.
"We've again grown the number of fully-funded New Entry to Specialist Practice (NESP) places for nurses to 230 annually including places for occupational therapists and social workers working in mental health and addiction.
"Since 2017 we've more than trebled the number of funded clinical psychology internships and boosted the payment interns receive by 40 percent."