A council is suggesting all its workers take a pay cut of 5.4% and in return work two hours less a week to help save £62m over four years.
Southampton City Council's proposals include senior managers but rather than a cut in weekly hours they would take five days unpaid leave each year.
Although about 250 jobs will also be lost, the council said a further 400 jobs could go without the pay cut.
A consultation is now under way. Unison said the plan was "devastating".
Royston Smith, leader of Conservative-controlled Southampton City Council, said: "Our savings proposals represent months of planning.
"We knew the spending review was coming, we knew it was going to be tough and we planned for it to be tough.
"Some services will be reduced and some will go altogether. We will have to make difficult decisions and we will have to focus on services that are valued most by residents and businesses."
The local authority added that extra investment will be made in road and pavement repairs and in the care of vulnerable children.
But Steve Brazier, from Unison's Southampton district branch, said: "The cuts are pretty draconian.
"I think it is a devastating proposal for both the people who use the services and the workers."
An emergency meeting of all union members is to be held on 24 November.
Mr Brazier said strike action has not been ruled out.
The staff consultation will last 90 days.