Volunteers who have been trained to save lives by Staffordshire Ambulance visited the House of Commons to protest against plans for a giant regional service.
More than 100 community first responders called for Staffordshire Ambulance to be allowed to continue.
The Government is conducting a review which is expected to recommend the merger of four existing services - Staffordshire, West Midlands, Coventry and Warwickshire, and Hereford and Worcestershire, into one huge service called Central West Ambulance.
But MPs from all parties have condemned the plans, pointing out that Staffordshire has the best response times in the country. Merging it with other services which are less successful would result in a decline in performance and put lives at risk, campaigners say.
Yesterday's demonstration at Westminster involved community first responders - volunteers who help provide emergency medical treatment.
They are sent to medical emergencies while ambulances are on the way. Community first responders, who attend a six-month training course, are able to use defibrillators to treat heart attacks, administer drugs and treat traumatic injuries.
Yesterday they delivered a petition of 1,500 signatures protesting against the merger to MP Charlotte Atkins (Lab Staffordshire Moorlands), who met Tony Blair to ask him to save Staffordshire Ambulance.
She said: "I don't believe it is a done deal. A lot of people say the merger is done and dusted but I don't accept that."
Health Secretary Patricia Hewitt has insisted no decision had been made on whether to merge ambulance services - but has also announced that a new trust will start on July 1.