Londonderry looks set to lose its Community Crisis Intervention Centre (CCIS) after the Health Minister confirmed his department would not provide any further funding.
Foyle MLA Mark H Durkan, who received the information in a response to a letter to Robin Swann, said the decision will be challenged in the city which has the highest suicide rate in the UK.
Mr Durkan said the decision was contrary to Mr Swann and the Executive's repeated commitments to improving mental health services across Northern Ireland.
The CCIS, operated by social justice charity Extern, was set up in Derry 15 months ago. It operates from Thursday evening to Monday morning for people in crisis and has been a safety net for vulnerable people at risk of suicide.
The Department of Health funded the CCIS in Derry through funding from the confidence and supply deal between the Conservative Government and the DUP until March 31 as a pilot project.
This funding was continued for three months as an interim measure during the pandemic.
Mr Durkan said: "The stark reality of the future of the Crisis Intervention Centre in Derry has been apparent for quite some time. The crucial requirement for continued funding is one I have raised consistently with the department.
Platitudes won't wash this time - while we all welcomed and applauded the Executive for their supposed commitment to improving mental health, it would seem those promises are not being backed up by any credible actionMark H Durkan
"The need for this service is blatantly obvious - my constituency of Foyle has among the worst suicide rates across these islands.
"As such, the thoughtless decision not to fund will force its closure, consequences of which I fear will reverberate throughout our communities.
"Platitudes won't wash this time - while we all welcomed and applauded the Executive for their supposed commitment to improving mental health, it would seem those promises are not being backed up by any credible action."
River rescue charity Foyle Search and Rescue (FS&R) and Derry and Strabane Council called on Mr Swann to save the service. FS&R chairman Stephen Twells said the failure to fund the centre was "an absolute disgrace".
He challenged all government ministers to come to Derry and spend a weekend on patrol with FS&R volunteers as soon as the coronavirus restrictions permitted.
Mr Twells said: "The fact that money for the Crisis Intervention Service isn't included in the Department for Health's funding to address suicide prevention is an absolute disgrace. The fact that any department within Stormont isn't helping to fund this is a disgrace.
"Its not that the Community Crisis Intervention Service is believed to have saved lives in its pilot year - it has saved lives.
"We work very closely with this organisation, signposting those in need to them. They do make a difference and the service it provides is going to be needed even more as we come out of this pandemic."
Councillor Sandra Duffy said: "I believe the budget for the Crisis Intervention Service in Derry which is £215,000 is an amount of money the minister could find because in the grand scheme of things it isn't a lot, especially when you consider the lives it has already saved.
"It works really well and has saved lives in this city without a shadow of doubt so we need to ensure this vital service is retained."