Unions are warning workers from the NHS blood service may go on strike over potential closures of blood centres.
The NHS Blood Service coordinates blood supplies
Amicus has warned it will ballot for industrial action if the NHS Blood and Transplant Authority goes ahead with plans to create regional centres.
The service's 14 blood centres in England collect and screen the 2.1 million donations given each year, supplying hospitals with stocks.
Under the proposals, the centres may be replaced with three "super" centres.
It is unclear how many jobs will be lost under the changes, which are to be phased in over the next five years.
Kevin Coyne, Amicus's national officer for health, said: "Modernisation is being rushed through without engagement and consultation with either staff or local communities.
"Furthermore, hundreds of technical and scientific staff jobs are being put at risk and these highly skilled jobs cannot just be recruited or relocated to different parts of the country.
"The NHS and the nation has invested millions in training these staff and now proposes to just dispose of them.
"The geographical gaps in service will also mean delays for the vital testing of blood for many thousands of people, putting lives at risk and making the service dependent upon a charity - air ambulances, in emergencies as motorways cannot be relied upon."
The threat follows the first national strike in the health service last month when staff from the NHS Logistics supply agency walked out over the transfer of the body to delivery firm DHL.
The NHS Blood and Transplant Authority, which runs the blood service, said the service was costing the health service more money than it should and several of its centres were "unsuitable" for modern processes.
A spokeswoman added: "We are planning a number of steps that will help the organisation meet the challenges ahead and ensure that it can continue to deliver the high-quality services on which patients rely.
"Many of the plans are still being developed, and as a result we cannot accurately predict what the overall impact will be for staff, but overall headcount will go down.
"The proposed changes will take place over several years, and so we will try as far as possible to avoid compulsory redundancies."