National has made a supermarket break-up a key part of its election pitch, proposing to sever Pak'nSave from New World in a bid to drive down grocery prices.

National's plan would turn the company into supermarket chains: Pak'nSave, New World/Four Square and Woolworths.

The breakup, however, would be contingent on a six-month review by the Commerce Commission into whether the split would leave shoppers better off.