Supporters of two hospitals where the A&E hours are expected to be slashed say the move could be devastating.
It emerged yesterday that opening hours may be cut at both the Downe and Lagan Valley Hospitals by the end of this month.
The South Eastern Trust confirmed that it was an option because of a critical shortage of medical staff and said a decision would be announced later this week. Officials for the trust met Department of Health officials on Tuesday, but missed seeing Health Minister Edwin Poots.
A department spokesman said the minister was in Londonderry fulfulling prior engagements.
DUP Lagan Valley MP Jeffrey Donaldson said he was disappointed at the development, describing it as "neither efficient nor effective".
He also revealed that Mr Poots was "very annoyed" at the situation and said that he had taken part in a high-level meeting yesterday to find a solution.
Chairman of the Down Community Health Committee Eamon McGrady said the news was a "devastating shock" to the local area, pointing out that the largely rural population depended on the hospital provision in Downpatrick.
He described any potential cut to services as "dangerous".
Mr McGrady said the cuts were expected to be brought in on December 28, which leaves little time to battle. But he promised a "very active campaign against the cuts".
The committee played a role in securing the new Downe Hospital, which was opened in 2009.
A spokeswoman for the South Eastern Trust said officials were looking at options for emergency care services at both sites.
"The South Eastern Trust is experiencing a critical shortage of medical staff in both the Downe and Lagan Valley emergency departments," she said.
South Down MP Margaret Ritchie vowed that "any attempt to dilute services at the Downe Hospital will not be tolerated".
NI21 MLA John McCallister said he was appalled by the news and felt let down by the trust.
The matter was discussed at a meeting of Down District Council last night where councillors demanded a meeting with the Health Minister.