A Ministry chief executive is refusing to say whether Immigration Minister Iain Lees-Galloway used his discretion correctly in regard to Karel Sroubek's residency.
Last year, Sroubek - a convicted drug smuggler - had his deportation liability cancelled by Lees-Galloway, who was criticised after revealing he only spent "about an hour or so" to make the decision.
The Minister later reversed his decision when new information about Sroubek came to light which hadn't been included in his briefing file. That prompted a review of Immigration NZ's processes, which Mike Heron QC reported back on on Wednesday.
Along with Sroubek's file, another 29 complex case files were reviewed by Heron. He found that all 30 case files were drafted fairly and objectively by INZ.
Among several recommendations, the report suggested decision-making powers should be given to immigration experts rather than ministers as officials have more time and expertise. The Immigration Minister should also be able to request more advice in complex cases, the report said.
While the report focused on Immigration NZ's role, National's justice spokesperson, Mark Mitchell, said the report showed Lees-Galloway was incompetent.
"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," he said in a statement on Wednesday.
But the Ministry of Business, Innovation and Employment (MBIE) chief executive, Carolyn Tremain, is refusing to make a judgement on how Lees-Galloway dealt with Sroubek.
It is not for us to determine whether it was a good or bad decision.
"He exercises absolute discretion in that decision-making process... I'm not going to comment on that," she told The AM Show on Thursday.
"His decision is the final decision."
She said the Immigration Minister has to deal with a wide range of cases, but there would be a discussion with Lees-Galloway about which ones made their way to his desk for his consideration.
"The cases range quite significantly in complexity, and there is no doubt that this particular case was one of the most complex for the Minister to work with," Tremain said.
Prime Minister Jacinda Ardern was willing to defend the Minister on Wednesday, saying she had confidence in him and he was just following "a process that existed for years".
"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."
She said the Heron report "rightly suggests the whole process needs to change because both Immigration NZ and ministers were carrying too much risk".
Lees-Galloway said on Wednesday he's since made changes to the process that he uses.
Sroubek was convicted in 2015 of importing almost 5kg of MDMA into New Zealand and he was sent to prison for almost six years.
He was denied parole last month.