The trusts want to establish “wholly owned” private companies to take over a range of services, such as portering and pathology.
The plan involves the transfer of jobs out of the NHS and into the private companies to save cash.
But public service union Unison says similar projects in the past have led to cuts in pay and worsening conditions of workers who are already low-paid, and also to the creation of management jobs with bloated salaries.
Unison regional head of health Tony Pearson has written to chief executives and senior managers in West Yorkshire warning that the union will lead community campaigns against the plan.
“We have seen that over time pay and conditions for our members transferred to private or ‘third sector’ organisations have been eroded and ultimately ‘harmonised’ with those of new employees coming in on inferior terms,” he said.