Some of the country's top constitutional experts are raising red flags about the Government's attempt to entrench part of its Three Waters reforms.

Under a change proposed by the Greens, and supported by Labour, 60-percent of MPs would need to agree to overturn part of the bill protecting water assets from private ownership.

Eight public law academics have written to the Government, saying such use of entrenchment sets a dangerous precedent.

Until now, entrenchment has only been used for electoral laws that specify how electorates are drawn up, the method of voting, the voting age, and the length of the Parliamentary term.

Timaru Mayor Nigel Bowen —an opponent of the Three Waters reforms— told Kate Hawkesby that it's a worrying development.

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