The Finance Minister says the National's bid to break up Foodstuffs would be the most low-cost measure to ensure Kiwis can get cheaper groceries.

National is campaigning on separating Pak'nSave from New World and Four Square - if the Commerce Commission believes it stacks up.

Nicola Willis says there's less benefits and more costs around restructuring Woolworths, as the retailer would have to set up an entirely new operator and brands.

"Whereas, Foodstuffs already has two different brands, it already has Pak'nSave vs New World. So the costs of that restructure are lower - and once you add in all of the extra costs of the Woolworths restructure, you end up with lower net benefits."

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