The Labour Party will be forced to vote against the Trans-Pacific Partnership (TPP) as it stands after the government confirmed it would put the planned law changes into one overall bill.
Trade Minister Todd McClay will table the TPP and the analysis supporting it in Parliament on Tuesday, kicking off the parliamentary process to ratify it.
A number of law changes are needed, including to tariff, copyright and patent rules.
Mr McClay will use what is called an omnibus bill to push it through Parliament, which will force Labour to vote against the bill rather than pick and choose the bits they support.
Its trade and export growth spokesperson, David Clark, said Labour supported free trade, but it opposed the TPP since the agreement stopped any future government from banning house sales to foreigners.
"We will oppose any bill that undermines New Zealand's sovereignty. We've been clear on that from the start. If the bill is split up in the later stages we may have to look more closely at things."
The government expects to pass the legislation late this year or early next year.
All 12 countries have to ratify the TPP within two years, and the deal also needs the United States and Japan for it to come into force.
The agreement was signed at SkyCity in Auckland yesterday, with thousands of people taking part in protests against it across the city.