Water company Severn Trent plans to axe hundreds of jobs as part of a restructuring programme.
The Coventry based business, which employs around 6,000 workers, said there would be a "potential impact" of 500 job losses in its management and support sections.
But the FTSE 100 firm said it will create up to 100 additional front line roles as customer service remains its "number one priority".
"There are no plans to reduce the number of customer-facing front line operational roles in our customer care or wholesale operation," a statement from the company said.
"We have already had recruitment controls in place since July and are reducing the number of contractors and temporary resources.
"We will also seek volunteers for redundancy in areas where we need to lose roles.
"We are hopeful these measures will keep any need for compulsory redundancies to an absolute minimum."
The employer said it would work with the firm's unions, including Unison, GMB and Unite, during the process.
"We are in talks with Severn Trent and we are working to minimise the need for compulsory redundancies," said Stuart Richards, a regional officer at GMB.