The decision to evict a charity for children with learning disabilities from Hillsborough Castle should be reversed, MLAs have said.
The Georgian-built mansion hosts the Queen and other members of the royal family during their visits to the Province.
But the management of the grounds has been transferred to Historic Royal Palaces, which oversees other sites like the Tower of London and Hampton Court Palace.
The Praxis charity has been told it must leave its cafe and market garden within the grounds of the castle to make way for development aimed at boosting visitor numbers.
Sinn Fein MLA Jennifer McCann said: “Theresa Villiers and the NIO need to respect the rights of those who are vulnerable in society.”
A Sinn Fein motion at Stormont yesterday said the transfer of the publicly-owned assets at Hillsborough Castle should be conditional on securing the future of Praxis at this location.
The motion was agreed with no dissenting voices.
Ms McCann added: “It is often said that the measure of a progressive, caring society lies in its treatment of its most vulnerable citizens.
“I am calling on Theresa Villiers to ensure all the people who work at the Secret Garden at Hillsborough will continue to do so.”
The NIO has argued that the charity had enough time to make alternative arrangements; it was informed of the decision more than a year ago.
Seven staff and 16 people with learning difficulties work at the centre. Praxis said it had spent £400,000 developing a garden and coffee shop, but the NIO has turned down a compensation request.
The government department said the charity had benefited from extremely generous terms over several years at the site, including an annual rent of just £1.