Nottinghamshire County Council has said it is looking to make about 3,000 redundancies over the next three years.
The Conservative-led council said it had been forced into the move by the need to make savings of £150m from its annual budget of £484m.
Officials confirmed the majority of the authority's 12,000 staff would be consulted on voluntary redundancy.
Unison has condemned the move saying it is not about money but an attack on public services.
The council had already said 483 posts were to go this year, with an additional 1,000 at risk.
The local authority said predicted losses had increased from 1,000 to 2,500 in part because of the speed and scale of predicted government reductions.
Mick Burrows, chief executive of the county council, said the factors behind the cuts were still changing.
"One is the government grant situation, with possibly a 20% to 40% reduction in grant which will be disclosed later this year when the comprehensive settlements are made.
"Another is that inflation is increasing - we are seeing massive rises in the price of salt and bitumen for roads etc.
"And number three, which is quite significant for us, is the pressure on services, particularly children's social care, where we are seeing a massive rise in referrals to us."
He added that while the authority had an annual workforce turnover of 10%, compulsory redundancies could not be ruled out.
"It would be wrong of me to put a figure on it but when you look at the scale, let's be real.
"If we have the very worst case scenario on this three year projection of 2,500, I know we will not get that many voluntary redundancies but we should get fair proportion," he said.
Unison said the move was a risk for the wider local economy.
Andy Belfield, Unison spokesman for the East Midlands, said: "This is not about money, how can it be? The council has £100 million in the bank; it is trying to sell off services that make a profit and waste £50 million on redundancies.
"This is really about a Tory council that doesn't like public services and is trying to get rid of as many jobs and as many services as it can, regardless of the effect on people in Notts. Let's not forget that 2,500 jobs lost here will be 2,500 people who can't spend money in local shops."
Staff were told about the job losses as they arrived at work.
Letters will be sent out to the majority of staff from 16 August inviting them to make an expression of interest in voluntary redundancy.