The South Western Ambulance Service is withdrawing from its contract to provide urgent care services across Dorset - including the NHS 111 service.
Despite being given a 'good' CQC rating for NHS 111 in 2018, the service says it has 'struggled to maintain the staffing levels'.
The ambulance service says it only provides urgent care services in Dorset and other aspects of the service will not be affected.
A spokesperson confirmed: "Over the next few months, South Western Ambulance Service will be working with Dorset HealthCare University NHS Foundation Trust to agree a timetable for the transfer of services.
"Dorset HealthCare University NHS Foundation Trust will undertake a process to identify a new provider for urgent care services in Dorset, including NHS 111. The aim is to make sure that Dorset continues to have a locally run service operated by local staff – the local health partnership is committed to achieving this.
"As a committed member of the Dorset local health partnership, SWASFT and Dorset HealthCare University NHS Foundation Trust will work closely with all other members of the partnership to ensure we continue to provide a safe and reliable service for our patients and offer continued to support to the staff in order to achieve the best outcomes for everyone involved .
"Discussions are still at an early stage as to how and when this change will happen and more details will be shared when appropriate.
"SWASFT staff currently working on the Dorset contract have been informed of this decision and will be guided and supported through the transition period with full HR advice and Union consultations, together with one-to-one meetings."