More than 400 jobs could be lost at Bury Council as the authority seeks to save £28m over the next four years.
The council has begun a three-month consultation period, with the unions warning that 420 jobs might be shed.
Council leader Bob Bibby said: "This is not the number of jobs that will go, only the potential number in a worst case scenario."
The council will know the full amount it has to save next month when its government grant is revealed.
Mr Bibby said the authority hoped to reduce the number of compulsory redundancies through natural wastage, voluntary severance and early retirement.
But he added: "I hope that this will be enough to avoid making compulsory redundancies, but I'm afraid I cannot give any guarantees about that."
The council had said that it aimed to find £28m of savings over the next four years, starting with £7m in 2011/12.