Up to 800 jobs could be lost at Oldham Council as it battles to save about £45m in the next three years.
The authority said it needed to save £25m from the 2011-12 budget, and possibly a further £20m in 2012-13.
Trade unions are being consulted on the proposals, which the council hopes will be the start of a "constructive dialogue".
Staff were left "shell-shocked" by the announcement, said Unison branch secretary Julie Finnegan.
The local authority issued a notice listing all posts that are under review on Thursday.
Councillor Lynne Thompson, Cabinet Member for Performance and Value for Public Money, said: "This is a very serious step and one that we do not take lightly, but it is also unavoidable as we face up to the well-documented financial pressures affecting the budgets of every single UK local authority.
"These initial proposals are an opening basis for discussion and we want to engage in a meaningful dialogue with staff and trade unions.
"These are testing times but we must remain fair and consistent in our decisions, and mindful to minimise the impact these reductions will have on service users across the borough."
A review of other ways to reduce costs in areas such as procurement, accommodation and asset management - as well as minimising the use of agency staff - is also being carried out.
"The solutions may also involve buying in services instead of providing them, so some posts will be replaced with private sector jobs," she added.
The earliest that any compulsory notice will be issued is January 2011.
Mrs Finnegan said the council had ignored their proposals for alternative budget cuts.
"All our members within Oldham Council are absolutely shell-shocked," she added.
"We knew the cuts were coming but we obviously didn't anticipate this full amount."