Homeless support organisations and charities fear that £3m in funding cuts to a key housing support programme could threaten critical services for over 20,000 people in Northern Ireland.
The concerns centre on the Supporting People programme, which funds housing-related services for vulnerable people.
Its budget is allocated by the Department for Communities (DfC) but administered by the Housing Executive (NIHE).
While the DfC has maintained the scheme's budget at £72.8m for the 2017/18 financial year, the NIHE has written to the scheme's providers to advise a 5% reduction to some budgets.
Members of the Committee Representing Independent Supporting People Providers (CRISPP) say over 100 organisations must find total savings of £3m, putting services at risk.
They claim the funding cuts were implemented "without an assessment of performance quality nor the sustainability" of the programme's service providers.
Simon Community NI chief executive Jim Dennison said that while his organisation had "no plans at present to close hostels", they could "be forced into a position where we have no choice".
He said: "These are some of the most vulnerable in society and we are their safety net.
"If we scale back our services, where do they go? We have realigned programmes to maintain services, but can't plan for next year. We had hoped to take on new staff and trial new programmes on addiction and mental health. We would ask the NIHE to reconsider."
Ricky Rowledge, a co-chair of CRISPP, said: "Services cannot be sustained at the standard required and there is a very real danger that those in most need will not receive adequate support or may lose out entirely.
"We are calling for the NIHE to reinstate the funding immediately and work in partnership with delivery agents to agree a sensible reform and strategy for Supporting People."
A NIHE spokesman said they would "continue to work with providers to attempt to mitigate the impact" of the cuts.
"There are a number of inescapable new financial commitments which need to be met. This reduction will not be applied to floating support schemes," he added.