About 500 jobs are under threat as a council attempts to save up to £50m over the next three years as part of the Spending Review.
Dorset County Council made the announcement as part of proposals to save about £27m in 2011/2012.
A number of cuts to services including withdrawing funding from libraries and school crossing patrols are to be discussed by councillors next week.
The council said "front-line services" would be protected as far as possible.
Areas including administration and youth services are also expected to be affected.
The council said some funding could be saved by reducing the number of council buildings and increasing income from services like country parks.
Pamela Jefferies, from the union Unison, said: "We're absolutely devastated. We've been asking for figures for quite a long time now and haven't been getting any figures.
"That's 500 full-time equivalent, so that's going to be more posts even.
"There's going to be a lot of people affected."
Chancellor George Osborne announced a 28% cut in government funding to local authorities over the next four years as part of the Spending Review.
Last month workers from the public sector union Unison staged a mock-funeral procession through Dorchester to protest against the cuts.
Councillors are set to discuss proposals, which include withdrawing funding from up to 20 of the county's 34 libraries, on Wednesday, 15 December.
Also under threat are day centres, careers advice and school crossing patrols, which could be offered as volunteer roles.
A final decision will be announced in February.
Leader Angus Campbell said: "We are trying to focus on our core priorities in delivering services to the public, and particularly protect - as far as possible - those areas which deal with our most vulnerable residents.
"At the same time, we are also looking to work more closely with our communities, to try to safeguard other services and secure a viable future wherever we can.
"These are extremely difficult decisions we are facing. But, one way or another, we must find the savings."