The Commerce Commission has received several complaints from suppliers about their dealings with supermarket chain Countdown.
The confirmation yesterday came as Prime Minister John Key said any formal inquiry would be "very healthy" and establish whether claims of standover tactics by the company stacked up.
In Parliament last week, Labour MP Shane Jones said Countdown and its owner, Progressive Enterprises, had told some suppliers to make payments to cover the chain's historic losses on their products or they would be removed from shelves.
The commission has now had an official complaint from Mr Jones and is assessing whether to initiate a formal inquiry. It said last week that suppliers could come forward with information in confidence.