Hundreds of jobs could be lost at Lincolnshire hospitals over the next five years after bosses were ordered to make cuts totalling £75m.
The Department of Health has told health trusts to make savings because of the recession.
Gary Walker, chief executive of the United Lincolnshire Hospitals Trust, said there would be a recruitment freeze and fewer agency staff.
"Changes will be planned so that we can avoid compulsory redundancies."
He added: "We'll also have lots of people who retire or leave - that's about 600 people a year.
"So as people leave they won't be replaced in every circumstance.
"When I joined the trust two-and-a-half years ago there was a deficit of about £13m.
"We balanced the books and we repaid all our debts from that period.
"In the next 18 months to two years patients shouldn't notice a major difference on the frontline - we'll be trying to reduce bureaucracy and paperwork.
"After that it's difficult to say because we're trying to plan for that."
Carol Brown from Unison said the announcement had come as a surprise.
"We believe if there are any cuts to jobs it would have a detrimental effect on the NHS and we'd not only be calling on our members to campaign against it, we'd be calling upon the community as well because we believe the detrimental effect would be so great."