The head of the Productivity Commission says any changes in the law to crack down on anti-competitive practices in the shipping industry will need careful drafting.
A preliminary report from the commission in January suggested automatic exemptions from competition law for agreements among shipping lines be dumped.
The International Container Lines Committee says agreements that fix prices aren't a feature of the New Zealand shipping market.
And it says it is now concerned a crackdown could affect other agreements that help keep freight rates down.
Productivity Commission's chair Murray Sherwin says anti-competitive in the shipping industry is not always clear-cut.
He says any law changes would need to be carefully drafted.