The Red Cross is set to close its ambulance service in Northern Ireland.
The charity said its contracted patient transport service is no longer financially viable and will come to an end in April.
More than 20 members of staff will be affected by the move.
News of the closure has sparked "anger and upset" among staff, ambulance union GMB has said.
The Red Cross provides a wide range of services throughout the region, including non-emergency ambulance transfers, which helps to alleviate the pressure on the Northern Ireland Ambulance Service.
David Morison, operational lead for the Red Cross ambulance support service in Northern Ireland, confirmed the closure.
He said: "We have decided to close our ambulance support operation in Northern Ireland at the end of April because unfortunately the service is no longer financially viable.
"As a charity, we have a clear responsibility to make the best use of our resources and use them in the most effective and cost-efficient way possible."
Mr Morison said that other Red Cross partnership work will be unaffected by the closure.
"23 members of staff are impacted by the closure and are currently being supported through this process.
"We would like to take the opportunity to thank our dedicated staff who have provided a high quality and compassionate service to patients over the past two years," he added.
GMB organiser Michael Mulholland said GMB members in the Red Cross ambulance service are "angry and upset" at the decision to close the service.
Mr Mulholland accused the Red Cross of failing to respond to attempts by GMB to secure the future of the service.
"These are loyal, skilled and hard-working ambulance staff who are now facing a very unhappy New Year," said Mr Mulholland.
He added: "GMB is incredibly disappointed that Red Cross has failed to respond to our attempts to work with them collectively over recent months and concern for the future employment of our members who have assisted in delivering such a high quality service in Northern Ireland.
"We are further concerned about the process of consultation and would ask for clarity to enable us to offer our members the support required."