Lincolnshire County Council says it expects to cut up to 1,000 jobs in a bid to save £125m from its budget.
It said it expected to lose between 800 and 1,000 FTE (full-time equivalent) posts over the next four years.
Savings are being implemented mainly in social care for adults and in youth services after a government decision to cut funding to local authorities.
County council leader Martin Hill said the cuts were being implemented in the fairest way possible.
He said: "We could've just taken 25% cuts across the board. We've said 'no, we're not going to do that. We're going to protect the most vulnerable, whether it be children or adults or anybody else'.
"But there are some choices where those nice-to-do things which people would like to have and we'd like to continue to provide, we're going to have to take a more hard view on."
But John Sharman, of the union Unison, said staff would not take the news quietly.
He said: "One of the characteristics of people who work in these kind of jobs is that they do it because actually they've got a public conscience and they care about the service that they provide.
"So it's not just about the jobs, it's about what they actually provide. And seeing that big hit in the way that this budget will hit them, I don't think they will take that lying down."
The local authority expects to start a consultation with staff in January.