Lisburn City Council has called for a cafe run by a mental health charity to be allowed to remain in the grounds of Hillsborough Castle.
The Northern Ireland Office has asked Praxis Care, which runs the Secret Garden cafe, to leave.
It wants to make way for English charity Historic Royal Palaces to transform the castle into a major tourist attraction.
But some 15 people – many with learning difficulties – work at the Praxis cafe.
The NIO has so far refused to reimburse Praxis for the £400,000 it has invested at the site.
Last night, Lisburn council voted unanimously to back a motion proposed by DUP councillor William Leathem that Praxis should be allowed to remain at Hillsborough Castle.
Ulster Unionist councillor Alexander Redpath welcomed the vote and said there is strong feeling within Hillsborough in support of Praxis.
"I urge the Secretary of State Theresa Villiers to intervene to find a way for these two charities to co-exist at Hillsborough Castle," he said.