Bosses at Cornwall's main hospital have been condemned as "grossly insensitive" for failing to consult on plans that could see nearly 700 posts axed.
Unions say the possibility of sweeping reductions in the Royal Cornwall Hospital Trust's (RCHT) workforce over the next five years was a complete surprise, despite regular "bridge" building meetings.
Meanwhile, health campaigners have raised fears that the consultation paper, entitled Our People Strategy, will pave the way for hundreds of jobs to be outsourced.
Christine Dayus, regional organiser for Unison, said staff were "devastated".
She said: "Staff will be thinking 'here we go again'. We have been through crisis after crisis after crisis, while still providing high quality patient care, and yet this is how we get treated."
Ms Dayus said the trust had failed to let unions into the secret of what they were working on, despite assurances that all relations would be open and above board.
She said "absolutely no mention" was made of the strategy at a joint meeting held just a fortnight ago.
Failing to consult with staff was "grossly insensitive" and "completely outrageous," she said.
According to the paper to go to the board on Thursday, the RCHT is wrestling with increasing demands at a time of falling funding.
The trust is still paying off a £23 million historic debt while it seeks to trim £50 million off its £309 million budget in the long run.
The paper says that in order to get the right staffing mix by 2018, the "trajectory" of full-time equivalent posts could fall from a current total of 4,560 to 3,907 – or 653 posts.
Graham Webster, vice-chairman of the campaign group Health Initiative Cornwall (HIC), predicted a haemorrhaging of staff. "People aren't going to hang around," he said.
"The good staff will be off and our services will be the lesser because of it."
Moreover, he said the strategy suggested ancillary posts such as porters and cleaners would no longer be on the RCHT payroll.
This could only mean that a major outsourcing exercise was on the cards, he said.
"HIC is very concerned about this.
"Who is going to be cleaning the hospital, moving patients around and feeding patients?
"I suspect we are talking about outsourcing these services, which is the inevitable consequence of health reforms which seek to move increasing services into the private sector."
Jo Gibbs, RCHT lead for human resources and organisational development, said the exact size and shape of the RCHT's future workforce was not yet clear, but the trust would be working with its partners.
"In the next 5-10 years, the NHS will change significantly. RCHT must adapt and be flexible to meet the expectations of GP Commissioners and those patients using acute, community and specialist care services.
"Our People Strategy sets out how we aim to develop and shape our workforce using their talents and skills to be responsive to the health needs of people in Cornwall and the Isles of Scilly.
"We need to plan for new treatments, new technology and care delivered in different settings – with a greater emphasis on integration and partnership with other organisations."