The Government has been accused of misleading MPs and the public after claiming it had given Staffordshire a reprieve from merging into a giant Midland ambulance trust.
The Department for Health yesterday announced that Staffordshire Ambulance Service will be allowed to survive on its own but only "for up to two years".
The region's remaining three services - West Midlands, Hereford and Worcester, and Coventry and Warwickshire - will merge into a new body from July 1.
Ambulance trust mergers have been particularly controversial in Staffordshire, where the local service has the best response times in the country.
The county's Labour and Conservative MPs joined forces in a vocal campaign to save the trust, which attracted widespread public support.
Staffordshire will eventually join the new regional service and help it improve, Ministers said.
But Tory health spokesman Stephen O'Brien said: "It is a classic fudge, as it puts Staffordshire Ambulance Trust in the departure lounge."
Lichfield Conservative MP Michael Fabricant said: "Apart from my anger that the Government has tried to mis-lead MPs and journalists by implying that our ambulance service is saved, I am desperately alarmed that within two years, our award winning service will be no more."
Labour MPs welcomed the announcement that Stafford-shire would not be merged immediately as a victory for their campaign.
But David Kidney (Lab Stafford) warned: "If we get to the two-year anniversary and the improvements we were expecting in the new West Midlands service have not happened, I would expect MPs and the public to be in favour of keeping our trust separate."
Robert Lake, chairman of Staffordshire Ambulance Service NHS Trust Board, said: "We will continue to deliver high performance standards whilst working closely with other ambulance services, especially our excellent colleagues in the wider West Midlands, to play our part in making the ambulance service in England the envy of the world."
The new merged service will cover five million people in shire counties as well as cities such as Birmingham, Wolverhampton and Coventry.