Health bosses have denied patients were put at risk as medics struggled to deal with the number of patients turning up at one of Northern Ireland's busiest A&Es.
It comes after reports of chaos at the emergency department at the Ulster Hospital on Monday night – which resulted in patients arriving at the unit by ambulance having to wait for hours to be admitted.
According to the Northern Ireland Ambulance Service (NIAS), 10 of the ambulances that took patients to the A&E on Monday had to wait longer than two hours for their patients to be admitted – on two occasions they waited longer than three hours.
It is the latest crisis that demonstrates how overstretched the health service is across Northern Ireland and has raised further questions over emergency care provision here.
Kieran McCarthy, a member of the Stormont health committee, has called for immediate action by health bosses.
"I am very concerned by this unacceptable delay in admitting patients to the accident and emergency department at the Ulster Hospital," Mr McCarthy said.
"Ambulances are not meant to be tied up at the front door of a hospital, they should be responding to emergency calls.
"Lives are going to be put at risk if this problem is not resolved.
"The Health and Social Care Board should urgently look into what happened on Monday night and ensure that the resources are put in place so that it is not repeated."
The South Eastern Health & Social Care Trust has admitted the A&E, which has been struggling to cope with demand since the closure of the emergency department at Belfast City Hospital, was under particular pressure on Monday.
A trust spokeswoman said: "Patients were triaged as normal and on occasion had their treatment started whilst they waited for an appropriate space to become available in the emergency department.
"There is increased pressure on our staff who continue to provide excellent care to our patients under very challenging circumstances.
"Medical and nursing staff in the emergency department worked tirelessly to address patient needs at that time."
An NIAS spokesman said: "The trust recognises and appreciates the frustrations felt by staff, patients and carers as a result of these delays and would assure all concerned that we continue to work with colleagues throughout Health and Social Care to ensure that solutions can be found to this problem."
He said that while the delays experienced on Monday present a number of challenges to paramedics, the service has the resources to help them deal with such a situation.
The closure of the A&E at Belfast City Hospital has resulted in additional pressure on neighbouring emergency departments and the Ulster Hospital has been particularly badly affected. While additional resources were made available to help the hospital cope with the increase in A&E attendances, the number of patients turning up has been higher than expected. There has also been a greater than expected number of seriously ill patients who require admission to the hospital