Labour's yet to rule out the Green Party's plan to establish a publicly-owned supermarket chain, saying it has its own policy on breaking up the duopoly in New Zealand.It comes as both Labour and National defend their records on failing to bring down grocery prices, with all food groups recording price increases between May 2025 and May 2026.Speaking on Morning Report's political panel, co-host Ingrid Hipkiss asked Labour's Vanushi Walters what the party would do to even up competition in supermarkets.Walters responded only to say "New Zealanders really can't afford three more years of this government"."They've done not a thing to fix the increasing prices at the supermarket."Nicola's been talking a big game about a third supermarket competitor for probably more than 18 months now ... but the duopoly still controls more than 80 percent of the market for grocery prices."Walters said when Labour was in government it banned restrictive land covenants, enforced mandatory wholesale access and introduced a grocery commissioner as well."So we didn't just talk about change, we actually legislated for it."National's Nicola Willis.RNZ/Nick MonroHipkiss suggested those changes weren't effective in bringing prices down.Walters said the duopoly needed to be addressed, and Labour would release policy on that soon.National's Nicola Willis was quick to attack, saying she was astounded Walters didn't rule out the "Soviet-style nationalisation that Chlöe Swarbrick promoted at the weekend".Willis was referring to the Green Party policy that would aim to break up the duopoly and drive down food prices by establishing the publicly-owned chain, KiwiMart, that would be mandated to prioritise affordability.Foodstuffs and Woolworths would be forced to sell 120 stores and two distribution centres into public ownership which would require new legislation, Swarbrick said, at a cost of about $2.8 billion.Swarbrick referenced the likes of Consumer New Zealand as identifying "it does make sense to have a publicly-owned supermarket as a third competitor", during the announcement.Willis said on Wednesday the Greens wanted to "force supermarket owners to sell their supermarkets to the government"."And then she wants you to put her faith in her and Chris Hipkins to run a government-run supermarket line.Greens co-leaders Marama Davidson and Chlöe Swarbrick introduce the party's Affordable Kai policy, September 2026.RNZ"Now, last time I heard something this grandiose, it was called Kiwi Build, and it didn't work out well. Vanushi should just rule it out."Morning Report co-host Hipkiss asked Willis whether she'd given up on getting a third player to enter the market.In early 2025, the government had promised "meaningful change" in order to bring down food prices.Willis said at the time "all options" were on the table, and if competition failed to improve, ministers said they were even prepared to consider the "nuclear option" - forcibly breaking up the companies that dominate New Zealand's grocery sector.She promised to "pull out all the stops" for shoppers paying some of the highest food prices in the developed world.On Wednesday, Willis told Hipkiss she hadn't given up, and pointed to legislating fast-track capability for people to establish new supermarkets easier, "there are signs that we will make progress there"."However, we have continued to look at the structure of the supermarket sector because in the absence of a significant national player entering the scene, there is a question about how do you get the existing supermarkets to compete harder with each other."She said one proposal that had been discussed and looked at "carefully" was having Pak'n Save competing as a separate cooperative against Four Square and New World."That would effectively mean you'd have three main players in New Zealand."Walters countered this by accusing the government of removing the role of the grocery commissioner."By removing that referee, by removing that single point of accountability, you slow down any potential changes that can be made in this area. So effectively, they're taking us backwards."Willis said the powers of the commissioner would remain with the Grocery Commission, but admitted the role would no longer have a title.She also added the rise of food prices was "steadier" than under the previous government.