Labour MP Shane Jones says he will take his concerns about what he believes is extortionate behaviour by the Countdown supermarket chain to the Commerce Commission.
Using parliamentary privilege, Mr Jones told the House the Australian chain is blackmailing New Zealand businesses because of lower than expected profit margins.
Countdown categorically rejects the accusations and is inviting any suppliers with concerns to contact it directly.
It also said it would fully cooperate with any Commerce Commission enquiries.
The Food & Grocery Council said it is aware of a number of cases where companies have been asked for retrospective payments, and has raised that directly with the company involved.