The Government wants to crack down on anti-competitive behaviour and monopolies.
Commerce and Consumer Affairs Minister Kris Faafoi on Saturday announced he'll be asking the public for ideas on how to toughen the law.
"New Zealand has a high proportion of markets that are dominated by powerful firms, so it's important we have effective laws that prevent them from misusing their power," said Mr Faafoi.
"Section 36 of the Commerce Act is intended to prevent businesses from using their market power to suppress competition. However, as currently drafted, section 36 has tilted the playing field in favour of powerful firms and distorted competition.
"The law is difficult to enforce, and is not currently capturing a wide enough range of anti-competitive conduct."
Mr Faafoi gave an example, saying when a supplier asks a retailer not to stock a competitor's product, it's "unlikely" to be against the present law, despite being anti-competitive.
He said National was aware of the law's shortcomings, but failed to act.
"Nothing was done to protect consumers and honest business."
A Ministry of Business, Innovation and Employment review of the Commerce Act in 2015 and 2016 found opposition to change from big companies like Air New Zealand, Genesis Energy, Spark and ANZ, and business interest groups like Retail NZ and Business NZ, the Listener reported.
Those in favour of change included 2degrees, the Motion Picture Association of America, the Food and Grocery Council and the Commerce Commission.
At the time, then-Commerce Minister Paul Goldsmith said change was a priority, but changing the law would be complicated and officials would have to proceed in a "pretty cautious way", the NBR reported.