The decision to evict a charity for children with learning disabilities from an official residence of the Queen should be reversed, politicians in Northern Ireland said.
The Georgian-built Hillsborough Castle hosts the Queen and other members of the royal family during their visits to the region.
It is Northern Ireland Secretary Theresa Villiers' sprawling home when she is in the country and has been the site of many gritty political negotiations.
But the management of the magnificent mansion is being transferred to another organisation amid reductions in the NIO budget.
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 Stormont MLA Jennifer McCann said: "Theresa Villiers and the NIO need to respect the rights of those who are vulnerable in society."
A motion in Stormont's devolved assembly today said the transfer of the publicly-owned assets at Hillsborough Castle should be conditional on securing the future of Praxis at this location.
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.
Running of the castle is being transferred to Historic Royal Palaces, which oversees other sites like the Tower of London and Hampton Court Palace .
The NIO has said it has neither the finance nor the professional expertise to continue managing the site and enable its full potential to be realised.
It has added that Historic Royal Palaces' plans for Hillsborough mean the house and gardens will be enjoyed by more than 200,000 visitors each year, with scope for a range of charities to use its facilities.
That means, in the Government's view, Praxis must move out to allow the building of infrastructure.
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 late Georgian mansion was built in the 1770s by Wills Hill, first Marquis of Downshire and was later remodelled in the 19th and early 20th centuries.
Its gardens include 98 acres of ornamental grounds, peaceful woodland, meandering waterways, and trimmed lawns.
Sinn Fein's motion was agreed with no dissenting voices.
Ms Villiers said she deeply appreciated the work that Praxis Care has done for people with learning disabilities in the Hillsborough area and the contribution the charity continues to make to the community in Northern Ireland.
She added: "So I understand that many people are concerned about the current situation. But it must be recognised that continuing the status quo at Hillsborough Castle was simply not an option. The NIO has neither the finance nor the professional expertise to manage the Castle and enable its full potential to be realised."
The Northern Ireland Secretary said she was seeking the best option for the local area and for Northern Ireland more widely.
Historic Royal Palaces took over responsibility for the management of the castle and its grounds at the beginning of April.
She added: "Their five-year development project will see them working with local residents and a range of community groups, and they have stressed that their aim is to open up Hillsborough Castle to the widest possible audience.
"This vision involves inevitable changes to the estate, in order to improve the premises, increase visitor numbers and generate economic growth."