A consumer advocate's vowing to hold the Grocery Commissioner's feet to the fire on a shakeup to the supermarket duopoly. 

A new lobby group's being formed, driven by the former Consumer New Zealand Chief Executive, Sue Chetwin. 

It comes after struggles with The Warehouse supply of Weetbix and the fall of potential third player, Supie. 

Chetwin wants to see action happening faster, telling Tim Dower that the Commerce Commission's found we aren't being treated fairly when we shop at the supermarket. 

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