In its first piece of legislation, the new Minns government will amend the Constitution Act 1902 to protect Hunter Water and Sydney Water from privatisation.

Both utilities are statutory state-owned corporations and can be protected from being sold-off with an amendment to the Act.

The amendment would require Hunter Water and Sydney Water to remain publicly owned and would be binding for future governments - an Act of parliament would be necessary for their sale.

"We've seen what 12 years of privatisation of electricity network, ports and toll roads has done - it's led to people having to pay higher prices to pay for services they use to own," Premier Chris Minns said.

"This ends this week."

NSW Treasurer Daniel Mookhey said the state's economy has had a "short-term economic reliance on privatisation".

"That will end, and the first step is safeguarding the public ownership of Sydney Water and Hunter Water," he said.

"The Bill will act as an effective safeguard on the sale of state-owned assets, limiting the government's ability to sell off assets."

Water Minister Rose Jackson said the two utilities had been in operation for more than 130 years.

"They provide critical drinking water and crucial infrastructure and profit is directed back into the NSW government - it is basic common sense to keep these entities in public ownership," she said.

"These two entities were created on behalf of the people of NSW and this Bill will ensure they continue to operate in the best interests of the people of NSW."

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