Simon Bridges warns National won't support a controversial UN agreement on migration and will pull out if Jacinda Ardern signs up to it.
If adopted, the Global Compact on Migration would create a non-legally binding way of addressing why people migrate, how to protect them, how to integrate them into new countries, means of returning them home and other issues.
The agreement, which the Green Party is supporting, would "enable all migrants to enrich our societies through their human, economic and social capacities," according to the UN.
- Government won't commit to pulling out of controversial UN migration agreement
- Revealed: The Government's first immigration changes to 'help' students
- Govt may change immigration settings to take climate change refugees
But the National Party leader says his party "cannot accept this" as it could restrict New Zealand's ability to set our own migration and foreign policy.
"Immigration policy is solely a matter for individual countries and must take account of their individual circumstances," he said on Tuesday.
"There is no automatic right to migrate to another country without that country's full agreement, a view which the United Nation's Global Compact on Migration, set to be signed next week, seeks to counter.
"While not binding, the Compact could restrict the ability of future governments to set immigration and foreign policy, and to decide on which migrants are welcome and which aren't."
The Government is still deciding whether it will support the pact, with the Ministry of Foreign Affairs and Trade (MFAT) telling Newshub last week a final decision will be made before the adoption ceremony.
But the Coalition Government's confidence and supply partners, the Greens, are very clear they believe the Compact is of utmost importance to the international community.
"It is paramount that New Zealand, a responsible international citizen, be part of the cooperative solutions initiated by the Compact," Green Foreign Affairs spokesperson Golriz Ghahraman told Newshub.
Ms Ghahraman said the Compact both recognises the individual sovereignty of each nation, as well as the "vulnerabilities of migrants and the need to protect their human rights at all stages of the migration process".
"The alternative is the violent and shameful approach displayed right now by the US, and enabled by the Mexican governments to the 'migrant caravan' seeking asylum."
Several countries have already pulled their support, including Australia and the US. Australian Prime Minister Scott Morrison said there were concerns the Compact may be used to "undermine Australia's strong border protection laws and practises".
"The Compact fails to adequately distinguish between people who enter Australia illegally and those who come to Australia the right way, particularly with respect to the provision of welfare and other benefits," said Mr Morrison.
Mr Bridges says it's a sign we also should make our own decisions and refuse to sign up.
"While a number of countries are pulling out of the agreement as the extent of its potential impact on the decision-making of individual countries is realised, our Government is refusing to outline its own position," he says.
"For these reasons, National will not be supporting this agreement and we will reverse the decision if this Government signs up to it."