Unions are warning frontline services will be affected and jobs lost after Norwich City Council confirmed £3m cuts in the next financial year.
The council's executive said up to £15m would have to be saved over the next four years.
It is halfway through consulting with its 957 staff over job losses.
Unison said it had not ruled out strike action and added that the more jobs that were lost the greater the impact on frontline services.
Strike action possible
The council said £3m represented a cut of 12% to its budget for 2011-2012.
Deputy council leader Brenda Arthur said: "We have been looking at back office savings and have recently entered into a venture with the county council in terms of legal provision so we are looking at many ways we can make efficiencies."
But Kevin O'Grady, branch secretary of Norwich City Unison, said cutting back room staff would increase the workload on frontline workers.
He said they may eventually be forced into taking strike action "which is obviously something that nobody wants to do".
In June the council predicted 100 posts could go if it was forced to make cuts of £7.5m over two years.
The authority has pledged to avoid any compulsory redundancies.