The National Party says the government should not support a United Nations migration pact due to be signed in Morocco this week.
UN member states are meeting in Marrakesh over the next two days to formally approve the non-binding pact, which aims to increase global cooperation over migration issues.
National Party leader Simon Bridges said New Zealand should not sign up because we already have "good, if not excellent" immigration policy.
"Why would you mess with that ... why should we - in fact we shouldn't - do anything other than have independent migration and foreign policy and it seems to me that this will get in the way of that," he said.
Mr Bridges questioned the point in signing up to the pact if it were truly non-binding.
"It is creating a situation where we know even if it is not binding, over time it will become part of our laws, it will become interpreted by the judiciary. We don't need to do that. What part of our settings is wrong in immigration and why would we cede this?"
US President Donald Trump pulled his support for the pact a year ago, and in recent months other nations have followed including the governments of Australia, Austria, Israel and Switzerland.
If New Zealand were to reject the pact it would be in "good company", Mr Bridges said.
"Australia, the US, many EU countries... These are great, traditional friends of ours... I do this for our own reasons. But I think there's this view out there that this is some strange thing we are doing. We've got good [immigration] settings and it's the right thing to do."
New Zealand is sending UN representative Craig Hawke to Morocco for the signing.
Foreign Minister Winston Peters said his job would be to communicate New Zealand's position, get clarity on the contentious points and work out whether there was an appetite for change if it happened to conflict with the country's interests.