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.
A commission spokesman told the Herald the watchdog had now had "a small number of complaints regarding alleged anti-competitive behaviour by Countdown towards their suppliers" since Mr Jones raised the issue.
"These complaints will be assessed alongside the complaint made by Mr Jones."
Mr Key said yesterday that his Government had encouraged the commission to begin a formal inquiry.
"My view is it's very healthy to have the inquiry. Let's have a look and see what comes out of it."
A Countdown spokeswoman yesterday said it would "participate fully with any inquiry from the Commerce Commission". The company would have to see the detail of the concerns raised before commenting.