Managers at the Royal Cornwall Hospital's Trust have announced a plan to cut £7m from their budget.
The hospitals trust announced it was to cut 300 jobs
Proposals include employing fewer agency nurses and setting up a management panel to identify further cost saving measures.
The trust is predicting a £31m deficit and has employed accountants to prepare what it calls the Turnaround Plan.
Unions say they are concerned about the effects on staff morale and how the rest of the deficit will be dealt with.
Under the trust's plans, more outpatient and day-care would be introduced to save money on inpatient costs.
The trust said it would try to discharge patients more quickly with follow-up treatment carried out at home by nursing and medical teams.
The surgery process will also change so that essential tests are carried out just before an operation, freeing up pre-admission beds.
The hospitals trust announced in March that 300 jobs were to go to try and stem the projected overspend.
Unions said that staff were feeling worried, angry and demoralised.
Christine Dayus from the union Unison said: "Managers knew about the problems in March. Why have they waited until now to bring in measures to try and save money?
"Also, it does make you wonder where the remainder of the money is going to come from. They've got to find it, because the government and the Strategic Health Authority are being absolutely clear about that, and that's another worry."
The trust claims its money-saving plans were in harmony with the government's plans to modernise the health service.