The Association of Salaried Medical Specialists says a merger plan for the Otago and Southland district health boards is being rushed.
The union says that the views of doctors and nurses have been disregarded and that the process is too important to be rushed
Doctors and nurses in Southland are opposed to the plan.
On Thursday, the Southland DHB joined its Otago counterpart in approving the proposal, which now goes to Health Minister Tony Ryall for a final decision.
The boards say that they consulted widely and well, and that without a merger they cannot make progress with attempts to more closely align services.