She was asked by Stuff if the supermarket sector could be the next to be looked into.
"Other areas around the cost of living have been raised ... I wouldn't be surprised if we see a nomination in other areas like that."
"Particularly, when New Zealanders compare what happens in Australia, Kiwis say, 'Why are we seeing that marked increase here?'"
New Zealand's supermarket sector is largely made up of Foodstuffs, which owns New World and Pak'n'Save, and Woolworths, which owns Countdown.
According to the legislation, an MP would have to nominate the supermarket sector to be investigated by the Commerce Commission.
A spokesman for the Prime Minister told the Herald that other areas around the cost of living had been raised, and she wouldn't be surprised if there were nominations in other areas or industries.
"At this stage, the Government has no plans for market studies until the Bill is passed and we have been clear the first industry to be looked at is the fuel industry. There is no commitment to look at the supermarket sector at this time."