Workers in the NHS Blood Service in Birmingham could take their first industrial action in a row over jobs.
Union Amicus said plans to close 14 centres in England threatened the loss of hundreds of highly skilled technical and scientific staff.
The union complained that the changes were being made without proper consultation.
A lobby of MPs is being planned and Amicus said it will ballot 2,000 workers for industrial action if the closures go ahead.
A spokeswoman for the NHS Blood Service said talks had been held with the unions for a number of years about planned changes which will include moving the processing and testing of blood.
The changes were being planned partly because some facilities were in need of being upgraded and partly because there was less demand for blood.
She said the service hoped to avoid compulsory redundancies.