Legislation enacting the Trans Pacific Partnership Agreement is missing crucial Treasury analysis, Labour says.
The trade deal was signed by 12 nations in New Zealand in February.
The bill makes changes to several acts, such as extending copyright terms and introducing regulations so investment screening thresholds can be raised for overseas investors.
It does not include the Treasury's regulatory impact statement on the TPP, which Labour says is crucial analysis.
Labour's trade spokesperson David Clark said that indicated the legislation had been rushed.
"Treasury says further work is needed with stakeholders to ensure the proposals are workable and that unintended consequences don't result. That is a pretty serious concern. If the Treasury is worried that the legislation being introduced to Parliament is not even workable potentially, we have a serious issue here."
The bill has been introduced three weeks sooner than the government planned, so it can pass it by the end of the year, Mr Clark said.
