Jacinda Ardern is defending the Immigration Minister over his admission last year that he spent "an hour or so" reading a convicted drug smuggler's immigration file.
The Prime Minister said Iain Lees-Galloway was simply following a "process that existed for years", and said the entire process needs to change so the same thing doesn't happen again.
Her comments follow the release of an independent review by Michael Heron QC into Immigration New Zealand's (INZ) process for residence deportation liability decisions and how it can be improved.
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INZ is in charge of gathering files of information for the decision-makers who make residence deportation rulings.
The review relates to the Immigration Minister's decision in September last year to grant convicted drug smuggler Karel Sroubek residency in New Zealand upon the advice given to him by INZ.
Sroubek's case has been highly publicised ever since Lees-Galloway revealed he made the decision to grant the 38-year-old's visa "within about an hour or so" and without reading the full immigration file.
In justifying his initial decision, Lees-Galloway said last year Scroubek's life could be in danger if he returned to his home country, the Czech Republic.
But following the decision to grant the visa, Sroubek admitted he had travelled back twice to his home country under a false identity, which forced a U-turn from Lees-Galloway.
The minister said at the time the information about Sroubek travelling to the Czech Republic had not been made available to him when he made his original decision.
The independent review is now suggesting the Immigration Minister should be able to request more advice from INZ in such complex immigration cases.
Ardern told reporters on Wednesday it was a "complex case" and noted how the report "rightly suggests the whole process needs to change because both Immigration NZ and ministers were carrying too much risk".
"The process had always been that, based on the nature of the cases, Immigration NZ would bring the papers over and there'd be an expectation the minister would read and decide on the spot."
INZ agrees with the report's recommendation to provide the Immigration Minister with advice when requested, and said it will work with the minister to determine how it could provide further guidance.
"Because Immigration NZ was so focused on not being challenged, they allowed absolute discretion to mean for them that they weren't then offering direct advice or opinion to the minister," Ardern said.
"The way that this process was being managed is that the department would neither offer it nor wish to give it, and that won't be something people will understand - that's a process to change and it will."
National's justice spokesperson Mark Mitchell said he believes the system works, and that it was Lees-Galloway who "stuffed up".
"What we still don't have is a clear explanation from Iain Lees-Galloway about why he made this decision," Mitchell said.
"He accepted a convicted criminal at his word that he couldn't go back to his home country because of concerns for his safety.
"It's a shame that so much time and money has gone into this report just to tell us that Iain Lees-Galloway isn't up to the job."
Ardern said she has full confidence in the Immigration Minister.
Sroubek was convicted in 2015 of importing almost 5kg of MDMA into New Zealand and he was sent to prison for almost six years.