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Green Party co-leader Jeanette Fitzsimons has called on Fonterra to show some heart and challenged them to price milk and dairy products at a price New Zealanders can afford.

Speaking at the party's annual conference today, Ms Fitzsimons laid out a raft of food affordability policies the party planned to campaign on in the lead up to the election.

Among them, she queried why New Zealanders should have to foot increases in the price of milk which had resulted from global price hikes.

"Today I want to issue a challenge to Fonterra. Show us you are a good Kiwi company.

"Give something back to the country that has provided you with a great climate, cheap energy and hard working farmers that have allowed you to become so successful.

"Sell your products in New Zealand at a price our people can afford."

After her speech she said she had not yet put it to Fonterra, describing her call today as a "challenge" to the company.

"I would be happy to sit down with [Fonterra CEO] Andrew Ferrier at any time to discuss it. This is probably good timing, given their announcement yesterday."

Fonterra yesterday announced a record payout for farmers of $7.90 for a kg of milk solids.

While she did not expect the company to sell to the New Zealand market at a loss, she said the company could afford to make less of a profit on the four per cent of its products that were sold domestically.

"I do think a company that is based in New Zealand and has benefited from everything New Zealand has to offer in order to get established has got some responsibility back to this country.

"We are not asking Fonterra to sell milk at a loss, we're asking them to sell milk at a reasonable profit rather than an excessive one."

She said the reason for 60 per cent increases in the price of milk in New Zealand was because of the prices Fonterra could get in global markets.

However, she said New Zealanders were paying the higher prices because it was linked to the global markets.

"Families on low wages here have to compete with the wealthiest commodity traders and speculators of much larger countries to afford a product grown just along the road."

In a speech welcomed with rapture by the gathered membership at the conference in Auckland, she also said the party wanted a Commerce Commission inquiry to consider whether tougher competition law was needed to manage the supermarket "duopoly.

"When you've got two supermarket chains controlling 94 per cent of all the groceries, you have to ask if there is adequate competition, so it's quite a reasonable thing for them to investigate."

A similar inquiry was under way in Australia.

"It will investigate food prices and the growing gap between what the farmer receives and what the consumer pays. It may be we need a farmer to consumer code of conduct for supermarkets."

One option was to set up a "farmer to consumer code of conduct" for supermarkets to be held to, so that domestically produced foods were not subject to increases in global markets.

Ms Fitzsimons also advocated a return to more traditional styles of producing food, including government subsidies for communal vegetable gardens, farmers' markets and for schools to grow more fruit trees and vegetables.

She said benefits also needed to be adjusted by cost increases in "a basket of food, energy and housing costs", rather than indexed to the Consumer Price Index which did not fully reflect recent price increases in the basics.

She announced a "food revolution" based on a "coalition of the willing," made up not of guns and tanks, or hippies and activists but "an army of young mothers and older grandmothers - and yes men are allowed to join too - who will demand to know what is in the food they feed their children."