Hospital staff could strike over plans to change the way some workers are paid.
The Mid Yorkshire NHS Hospitals Trust is considering setting up a subsidiary company, to which the terms and conditions of employees would be transferred.
Non-clinical staff - those who do not deliver emergency care - would be affected.
A similar scheme is also being considered by hospital trusts in Leeds and Bradford. The trade union UNISON, which represents health workers, fears if the subsidiary company was taken over by a private firm, it would leave staff vulnerable to pay cuts and redundancy.
UNISON has entered into formal dispute with the Trust and say that they will take up the option to ballot members on industrial action if negotiations break down.
UNISON regional organiser Natalie Ratcliffe said members were “angry” at the proposals.
“They would create a two-tier workforce with people doing the same job as their colleagues but on worse pay and conditions.
“Our members know that a two-tier workforce will erode working conditions and shatter morale in the service. There is nothing to stop these companies being sold off again to other private companies. “
Mark Braden, director of estates, facilities and IMT at The Mid Yorkshire Hospitals NHS Trust, said: “Our Trust, like many across the country, is looking at different ways of providing services, including estates and facilities, so that they continue to be safe, high quality and more sustainable into the future.
“Our thinking about the creation of a wholly owned subsidiary is in the early stages and there is a long way to go before any final decision is made.
“There is more to do to explore the benefits and to get feedback from staff in those services before a decision can be made. We are committed to consulting fully with our staff on this along with our recognised trade unions.”