The Warehouse says the Grocery Commissioner needs to chop-chop on reform.

The retailer claimed an investigation into Sanitarium briefly stopping its supply of Weet-Bix isn't happening quick enough.

Sanitarium kept up supply to supermarkets.

Warehouse Chief Product Officer Tania Benyon says combined with online grocery startup Supie failing - it's reason for prompt action from the Commissioner.

"He should really use the powers that he has to stop that. We want a fair and level playing field, and he is the person able to do that."

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