Unison said the cuts show the 'impact of
One thousand council jobs could be cut by 2015, Wolverhampton City Council has announced.
The authority said the move was necessary to avoid a deficit of £89m by 2019. It has blamed cuts in central government grants.
Council leader Roger Lawrence said losing up to 20% of its workforce was "really bad news" for the city.
Unison said the news was "devastating" and would hit vulnerable people who depend on council services.
The Labour-controlled council has written to all its employees asking them to attend meetings at the civic hall where it will explain how it proposes to address the "current challenging budget position".
Mr Lawrence said: "When you look at all the effort we've put into getting the 1,400 JLR [Jaguar Land Rover] jobs, we effectively could face the entire benefit of that to the local economy being wiped out."
Opposition Conservative group councillor Neville Patten said the city council rather than the Government was to blame.
"Labour has come back into control and right away they are back up to what they are very good at doing; spending the money but not looking to see what the consequences are," he said.
Unison said the cuts show the "impact of government-imposed austerity".
Regional secretary Ravi Subramanian said: "These job losses are going to be devastating for the people who lose their jobs, upsetting for vulnerable people who lose vital services, and will stop economic growth."
The government has said councils must tighten their belts to help pay off the deficit it inherited from Labour.