A total of 264 assaults on healthcare staff were reported in Northern Ireland in the last year.
The number of attacks is on the rise, up 25% (53) since 2012.
It has led to calls for a zero tolerance approach to thugs who target health staff.
In the 12 months to April this year, 104 assaults were recorded on A&E staff and 160 on members of the Ambulance Service.
The figures were revealed by Health Minister Michelle O'Neill in response to an Assembly question from DUP MLA Gordon Lyons.
Unison's Conor McCarthy said assaults impacted staffing levels because when a worker was attacked, they often had to take time off.
"It leads to a recruitment and retention problem. It becomes very difficult to recruit and retain staff," he said.
Mr McCarthy claimed assaulted staff weren't being protected by bosses as they were left to take legal action or seek compensation themselves.
This was made more difficult by the fact that the people who attacked healthcare workers often became patients.
"The response of the organisation to its staff being assaulted is very poor," Mr McCarthy added.
"The employer should be responsible for staff."
He said part of the problem was that workers were not being trained well enough in restraining techniques like MAPA (management of actual or potential aggression), particularly support staff. He added that although stronger laws would serve as a deterrent, the most important thing was adequate training and support.
"My concern would be the proper employer support and legal support," he said.
A breakdown of the figures shows the Belfast Health and Social Care Trust had the highest number of assaults on ambulance workers over the past four years. In the last year there were 75 assaults.
The RVH had the highest number of attacks on A&E staff - 28 last year.
Mr Lyons called for tougher laws. "There must be zero tolerance against attacks on our healthcare workers," he said.
"My colleague Paul Frew secured a change in the law earlier this year to ensure the punishment for those convicted matches that in the case of attacks on police officers and firefighters.
"However, we must send a very strong message right across society that we value these vital workers."