The Commerce Commission is ramping up efforts to disrupt the supermarket monopoly.
It says supplier charges and promotional pricing are reinforcing the dominance of Foodstuffs and Woolworths.
It's proposing a simplified grocery code, reducing the range of payments that supermarkets can charge suppliers.
Grocery expert Ernie Newman told Ryan Bridge that supermarkets are receiving billions of dollars in discounts - which largely aren't being passed on to consumers.
He says there's more money floating around in the sector than the Commerce Commission had previously identified.
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