New Zealand's Green Party unveiled a plan to break up the country's supermarket duopoly under which Woolworths Group (ASX:WOW) and Foodstuffs would be required to divest at least 120 stores into public ownership, according to a Sunday statement.

The Affordable Kai election policy also calls for the creation of KiwiMart, a publicly owned supermarket chain with a sole mandate of keeping prices down.

Additionally, the party wants supermarkets to be transparent about their price margins, is seeking a ban on excessive supermarket prices, and is also looking to introduce a mandatory pricing accuracy code including automatic compensation requirements when shoppers are overcharged.

Food costs in New Zealand have risen 29% over the last five years, and the two big supermarket chains "exploit their market power" to prioritize profits, the Green Party said.

It added that modelling estimates the cost of acquiring 120 stores and two distribution centers at NZ$1.3 billion, with an additional NZ$1.5 billion required to capitalize KiwiMart as a commercially viable competitor.

Woolworths declined to comment, while Foodstuffs did not immediately respond to a request for comment from MT Newswires.