Family doctors are calling on the public to join them in a fight against a new health centre destined for Hemel Hempstead.
The GPs want people to sign a petition against the centre, which they claim will be 'potentially catastrophic' for health care in the town.
Sixteen out of the 19 GP practices in Dacorum have declared they are against the centre in a show of resistance to NHS bosses not seen before in this part of the country.
The doctors claim the centre will spell closure for existing surgeries and provide worse care for patients.
The campaign involves posters, 750,000 leaflets and the petition, which will be delivered to Parliament.
The GP-led health centre will be open to anyone 12 hours a day and 365 days a year in a town centre location as part of a nationwide government initiative to make it easier for people to see a doctor.
But the Hemel Hempstead and District Locality Forum, which represents family doctors, says the centre is not needed because local surgeries are now opening at earlier and later hours.
The forum claims the new centre will be able to register 6,000 patients, which will draw patients and resources from existing surgeries like Fernville and Lincoln House.
Dr Mark Brownfield, chair of the forum, said: "If you're going down the route of a walk-in centre, patients are going to be going in there in isolation of their medical records to see GPs who don't know them.
"We have grave concerns about the safety of this.
"It's potentially catastrophic."
Dr Paul Heatley, of Bennetts End Surgery, said: "We have a system that has evolved over 60 years.
"It's highly regarded by patients. Do you really want to throw that out and take a leap in the dark?"
A tendering process is currently under way to decide who will run the centre, which opens in March next year, and it is understood a number of multinational companies and local GPs have submitted bids.
The health centre is expected to sit alongside the urgent care centre that will replace A&E in Hemel Hempstead next year.
Doctors fear smaller local bidders will be unable to compete with the economies of scale big companies can draw on.
Dr Brownfield said: "We don't believe these large health care organisations can deliver.
"They will be pursuing a business-based agenda, feeding their shareholders and their motives will be different from existing GP practices."
He added: "If enough people oppose them there is still a possibility they could be stopped."
A letter outlining the doctors' opposition has been sent to the Herts Primary Care Trusts (PCTs) and the Department of Health.
The campaign is backed by Dacorum Hospital Action Group, Dacorum Patients Group and MP Mike Penning.
Mr Penning said: "It will be another white elephant that's going to be dropped in Hemel because they know they were wrong to take our hospital away.
"Instead of having it imposed on us it should be the GPs and local clinicians who decide what we need in the town."
Anne Walker, chief executive of the PCTs, said: "I do not believe that a new health centre is a potential threat to quality.
"Patients have raised time and time again, the difficulty they have in getting an appointment with a GP.
"The health centre is designed to complement the GP services that already exist and to offer patients improved access to services."
YOU CAN SIGN THE PETITION IN YOUR SURGERY OR BY CLICKING HERE.