The NSW upper house has passed legislation to amend the constitution to preserve public ownership of Hunter Water and Sydney Water.
Premier Chris Minns promised during this year's election campaign to legislate to keep the two state-owned corporations in public hands, but the Coalition has accused Labor of running a scare campaign on the issue.
The amendments to the Constitution Act, passed on Thursday night, will require an act of Parliament to undo the privatisation protections.
The government agreed, with the support of the crossbench, to establish a parliamentary inquiry into "safeguarding and supporting" other regional water utilities.
Mr Minns said the legislation would "prevent unreasonable price spikes and ensure these essential assets will always belong to the people of NSW".
Minister for the Hunter Tim Crakanthorp said the privatisation of essential services had "dudded the Hunter".
"Hunter Water is a community asset charged with providing for the community, and its protection in our state's constitution will ensure that it will continue to do so," he said.
To see more stories and read today's paper download the Newcastle Herald news app here.