The head of the Productivity Commission has admitted 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 between shipping lines be dumped.
The International Container Lines Committee says agreements which fix prices are not a feature of the New Zealand shipping market.
And it says it is now concerned a crackdown could affect other agreements which help keep freight rates down.
Productivity Commission chair Murray Sherwin says what is and is not anti-competitive in the shipping industry is not clear-cut.
He says any law changes would need to be carefully drafted.