Lisburn City Council is seeking a meeting with the health minister over the reduction in opening hours of Lagan Valley Hospital's A&E department.
Edwin Poots announced an end to 24-hour A&E cover at the hospital two weeks ago.
On Monday night, members of the South Eastern Health Trust were "interrogated" by the council over the issue.
The trust has blamed the reduction in service on a lack of junior doctors.
Monday was the first day of the reduced opening hours for Lagan Valley's A&E department. The unit is now open from 09:00 BST to 20:00 BST each day.
SDLP Mayor Brian Heading chaired the meeting and said he was keen to address the issue.
"We have asked for an update on the situation at the Lagan Valley Hospital every four to six weeks," he said.
"All the parties will also be taking part in a delegation to see the minister and questions about the budget and junior doctors will be raised directly with him."
Mr Heading said that staff from the trust were given a tough time at the meeting.
"The representatives of the trust were interrogated for two hours by councillors over how we have got ourselves into this situation," said the mayor.
"They explained the unusual situation where there is a shortage of junior doctors.
"This problem of junior doctors and a lack of them has been highlighted over the last two or three years yet we are never able to find out who is involved in training or allocating the number of junior doctors to the hospitals."
Cover to midnight
Jill Stafford, an A&E consultant at the Lagan Valley hospital, said that patients would be adequately covered by services at the other hospitals in the area surrounding Lisburn.
Dr Stafford also stressed that patient care would not stop at 20:00 BST and that all aspects of the service were being monitored.
"Anyone who comes to Lagan Valley up until eight o'clock in the evening will be treated as if they had come at five o'clock," she said.
"We have rostered staff in until midnight to cover any patients who still need to be seen from the department from eight.
"That will be revised as we see how the demand needs. Yesterday, we had a busier day as we think people are already taking heed of the change of hours and coming to the hospital when the A&E department is still open."