There is a "crisis" in Muckamore Abbey Hospital, Sinn Féin's health spokesman has said.
Pat Sheehan met with 17 staff members on Sunday to discuss their concerns.
A review into the safety of vulnerable adults at Muckamore Abbey Hospital revealed that lives were compromised.
BBC News NI understands that more than 20 staff have been suspended and Mr Sheehan said the number of staff members on sick leave is expected to rise "because of the level of stress".
Speaking on the BBC's Good Morning Ulster programme, Mr Sheehan said: "There are serious staff shortages due to suspensions and there are a significant number of staff members off on sick leave.
"There is a lack of leadership in the hospital. I went to the RQIA (Regulation and Quality Improvement Authority) last week because a nurse, just seven weeks out of training, was being placed in charge of a ward at the weekend. This was in spite of a report which said most of the incidents took place in the evenings or at weekends."
"Our party had to go to the RQIA again in the last week because of serious concerns about staffing levels in the hospital."
One nurse at the facility also described the situation as being at "crisis point".
An RQIA spokesperson said it was involved in a meeting on Monday morning.
"The Belfast Trust held a planning teleconference with health and social care partners, including the Department of Health, Health and Social Care Board and RQIA, to discuss contingency arrangements to ensure the safe care of all patients at Muckamore Abbey Hospital."
Over the weekend, a psychiatric intensive care unit at the scandal-hit County Antrim hospital was temporarily shut due to a shortage of staff.
The Police Service of Northern Ireland (PSNI) and the Belfast Health and Social Care Trust have started investigations into Muckamore Abbey Hospital.
It is believed that police were called to the hospital on Tuesday as staff attempted to restrain a patient.
Staff had wanted to place the patient in the hospital's seclusion room.
But because of the investigations they were not able to and instead had to call police.
Staff say they are afraid to either restrain or use the seclusion room due to the recent adverse publicity.
The PSNI said its officers "attended a report of an incident" on Tuesday.
Last week a patient's mother a described the seclusion room in which her son was placed as a "dark dungeon".
'Patients moved to other wards'
The confidential report about Muckamore Abbey Hospital charts a series of catastrophic failings and outlines that there was a culture of tolerating harm.
CCTV footage, taken over a three-month period, shows patients being pulled, hit, punched, flicked and verbally abused by nursing staff.
A father, whose son is a patient at the hospital, said heads should roll after the damning review into the safety of adults with learning difficulties.
Some charities have said the future of the hospital is now in question.
On Tuesday, the top official at Stormont's Department of Health met some of the families whose relatives had been affected by the abuse and apologised to them.
Richard Pengelly said his department plans to move vulnerable long-term patients out of the facility by the end of next year.
The Belfast Trust said the decision to temporarily close the psychiatric intensive care unit had been made "due to staff absences".
"Our priority is to provide a safe service; to do this we have moved affected patients into other wards," added a spokeswoman.
"The families of those patients impacted have been informed."
It said that while the unit was closed the facilities could still be used "as and when required".
The trust said that health authorities and the healthcare monitoring body had been informed of the closure.