Methanex is pointing to the previous Government's energy policy as the reason why it's proposing to scale down

The country's largest gas user's plants are shuttered until late next month, while it's been selling gas to Contact Energy and Genesis Energy, during New Zealand's power shortage.

It plans to move from a two-plant operation to one, and lay-off staff - for the forseeable future.

Managing director Stuart McCall says policy settings since 2018 haven't been conducive to sustaining enough gas supplies for more than one plant.

He says it's a disappointing outcome and they're likely to lose many valued people.