Five Shoalhaven District Hospital security staff have been injured in six months and have not been replaced, according to the Health Services Union.
HSU organiser Mark Jay said staff were getting injured on a daily basis and were often in tears.
"All I hear is their concerns - about inadequate staffing, inadequate resources, not replacing staff when they're injured from an aggressive incident," Mr Jay said.
"They've said because of the lack of staff, they're put in the situation where there is only one security officer to assist with an aggressive situation.
"I've worked in health for 17 years ... morale has never been so low."
It's not the first time the union has raised concerns about security staffing.
Former Labor South Coast candidate and nurse Cr Annette Alldrick said other nurses told her they were scared for themselves and their patients.
"This week there were patients in the X-ray department overnight, cared for by one nurse because there's nowhere else to go," she said.
"It happens all the time and it's been happening for a few years now."
Asked what could be done about these problems before the new hospital is built, NSW Opposition Leader Jodi McKay did not give any solutions.
"The very first thing they can do is give us a start date and a completion date and make sure the money's in the budget," Ms McKay said.
"I was here three months ago, there was bed block and it's unacceptable."
The Illawarra Shoalhaven Local Health District was contacted for comment.