Wiltshire Ambulance Service is to merge with two neighbouring services in a bid to improve response times. The services hope to amalgamate with Gloucestershire and Avon following a consultation which started in March.
The Unison union says it is concerned it will mean large job cuts but the managers say the annual savings of �1m can be invested into front-line crews.
In August 2004, Wiltshire and Avon's ambulance services were given zero star ratings from the Healthcare Commission.
Gloucestershire's trust was given two stars out of a possible three.
The authority will now conduct a three-month consultation into the recommendations made by an independent report.
Reaching targets
The Avon, Gloucestershire and Wiltshire Strategic Health Authority (SHA) hopes to launch the new trust within the next 12 months.
Trevor Jones of the SHA said: "At the moment ambulances are restricted by county boundaries and that can affect patient response times."
Philip Selwood from Gloucestershire Ambulance Trust added: "Across the trust we are not achieving the targets so each of the three are falling behind and it's important that patient care is delivered in the best possible way across all three counties."
But Ian Whitter from Unison cast doubt on the plans, saying that it could lead to job losses.
"We recognise the importance of the money that would be provided but we are concerned that it might mean job losses which we cannot accept," he said.