Figures provided to the Otago Daily Times showed that there had been marked increases in assaults on staff.
In the Southern health district, the number of assaults requiring time off work had increased from 12 in January to June, 2022, to 26 in the same period last year.
In total, there had been 96 such instances in the Southern health district since January 2022.
It is understood many of those incidents were from Wakari Hospital.
The ODT has asked for a more detailed breakdown specific to Wakari Hospital.
Public Service Association chairwoman Fleur Fitzsimons said it was time for Wakari Hospital to start treating its staff fairly.
"The situation for workers at Wakari Hospital is concerning.
"Staff at Wakari, particularly in mental health wards dealing with more acute cases, are over-worked and rosters are not being filled properly.
"The pressure on staff working is real and needs to be fixed through safe staffing and faster recruitment when vacancies arise."
Ms Fitzsimons said the stress on staff was leading some staff to take sick days because of burnout.
"Safe staffing for employees also ensures safe conditions and high-quality care for patients."
"Every health worker at Wakari Hospital should be safe at work and not exposed to assaults, violence and the chronic stress of working in unsafe conditions."
In response, Health New Zealand Te Whatu Ora (HNZ) Southern director of operations Craig Ashton said staff wellbeing and safety was a critical part of delivering quality healthcare to New Zealanders.
"No level of violence is acceptable and our staff have the right to feel safe at work.
"We remain committed to maintaining and strengthening our specialist mental health and addiction workforce at Wakari Hospital."
Mr Ashton said in the past year, HNZ had employed the highest number of graduate nurses (18) into Southern mental health services compared with any previous year, including 11 at Wakari Hospital.
It also had five new registered medical officers in the Wakari team since the start of the year.
"Healthcare settings can be challenging environments where patients may exhibit unpredictable behaviour for a range of clinical reasons, including delirium, acute pain, medication effects, or underlying medical or mental health conditions.
"While it is not possible to eliminate all of these incidents, Health New Zealand has robust processes and escalation pathways in place to manage these situations, minimise the risk of harm and prevent further escalation."
It is not the first time the troubled hospital has been under the microscope.
It came under fire from the Office of the Ombudsman in two separate reports about a decade ago, which outlined the lack of resources for patients and carers, the outdated setting and the lack of solitary space.
Then-chief ombudsman Peter Boshier deemed it a "volatile environment".
The hospital is also in the middle of a $15 million refurbishment, which would bring ward 10A up to standard. The refurbishment is planned to begin in the middle of this year and take up to 12 months.
Ward 10A supports people over the age of 18 who have an intellectual disability and require assessment, care, and treatment in a secure hospital environment.
To ensure patients could continue to access services during this time, patients and staff would be temporarily transferred to ward 9A which is also due for a revamp.
Improvements to ward 9A will include refurbishment of the two intensive care unit rooms, an accessible bathroom and staff facilities.
