[...] supermarkets may put pressure on manufacturers/growers not to supply [...]
If they do, I think they will likely be in for a world of hurt under the Commerce Act, as that would be pretty blatant anti-competitive behaviour.
I wish them luck. Anything that might shake up our cozy little supermarket duopoly, and bring more choice into our market, has to be good for consumers.
It would be, and if they could prove it, they'd be in trouble.
Proving it, though, is the hardest part.
I know that a certain electronics retailer puts a lot of pressure on their suppliers not to supply other retailers, or that those supplier have just 'chosen' not to supply the other retailers with their products all of their own volition.