Edwin Poots has been blamed for a "crisis" at accident and emergency services in Northern Ireland.
A major incident was declared at Belfast's Royal Victoria Hospital on Wednesday due to a large backlog of patients at the A&E department. Some faced long waits on trolleys.
The blame has been placed squarely on Health Minister Edwin Poots by the Ulster Unionist Party, whose health spokesman Roy Beggs blamed recent "ill thought out" decisions to reduce services and an "abdication" of leadership by Poots.
He said: "It is my firm opinion that the widespread problems being encountered in A&Es are a direct response to poor decisions made by the health minister and the mismanagement of the (health) trusts."
He added: "Not only was the crisis on Wednesday night unfair on the patients who had to sit for hours on trolleys, but also for the staff who were expected to carry out their vital work under such difficult conditions."
Unison, the union representing hospital workers, said recent closures of emergency departments at other hospitals at weekends had compounded the problem.
Unison held a protest outside the Royal on Wednesday afternoon.
A spokesman said: "It is now clear that the drive to implement Transforming Your Care (reform package) by cutting, closing and privatising A&E departments while at the same time reducing bed numbers across our health service is putting patients at risk.
"We are now demanding an independent inquiry into the provision and delivery of A&E services in the Northern Ireland health service, given that it does not appear to be safe in the hands of those currently responsible."
The union claimed the recent closure of emergency departments at weekends in Lisburn and Downpatrick would "further compound the crisis".
A spokeswoman for Belfast Health and Social Care Trust said the emergency department at the Royal experienced extreme pressures on Wednesday and as a result the health authorities declared it a major incident, calling in extra staff at short notice to deal with particularly difficult situations.
"Our staff dealt professionally and quickly with a difficult situation and within a few hours had rectified the situation," she said.
"We would like to pay tribute to the staff who work in such a challenging and demanding environment. They work under significant pressure and at all times put the needs of our patients first.
"While we fully understand how frustrating long waits can be for patients and recognise that the situation was not ideal, all steps were taken to ensure patients were safely cared for."
Mr Poots said last night's circumstances were exceptional and it was important not to confuse an exceptional circumstance with overall performance in Belfast where waiting times have been demonstrating some improvement.
Due to the nature of the conditions suffered by patients the proportion of people attending hospital who were admitted was more than 40%, compared to an expected level of around 28%.
The position by this morning was much better, with no patients in the Belfast trust or any other trust waiting more than 12 hours to be assessed, treated and admitted or discharged.
The minister added: "Major incident plans are there for exceptional circumstances, whether that is for a very serious road traffic collision or a high volume of very sick patients turning up to the emergency department on the same evening.
"The Health and Social Care Board is working with trusts to ensure that effective escalation plans are in place to respond appropriately to any surge in hospital activity."
This includes being ready to expand hospital bed capacity and increase community care packages to support people at home. In addition, plans are being put in place to enhance GP out of hours arrangements.
The minister added: "It is also important that the public play their part by using emergency care facilities responsibly and appropriately. People should always consider whether they need to go to the A&E, or if treatment could be sought from minor injuries units, GPs or GP out of hours, or a local pharmacist."