Czech drug smuggler Karel Sroubek is now liable for deportation, a report by Immgration New Zealand has found.
Immigration Minister Iain Lees Galloway announced the findings of the review into Mr Sroubek's residency case.
"As a result of that review, Immigration determined that Mr Sroubek may be liable for deportation on grounds that I had not previously considered."
He said there was some information INZ compiled that was not available to him when he made his original decision.
"This included new information from InterPol confirming details of his convictions, the fact that he was present in court when found guilty and that he appealed the verdict to the highest court in the Czech Republic."
He said NZ Parliament’s law "set a minimum statutory bar on who is entitled to come to New Zealand, including certain criminal convictions".
"Mr Sroubek’s visas, both temporary and permanent residency were granted when his Czech convictions rendered him a person who was not able to meet that bar.
He said INZ did not know this, "because Mr Sroubek was using a false identity".
"This founds a new ground for liability under the Immigration Act 2009."
Mr Lees Galloway determined Mr Sroubek is now liable for deportation.
"The effect of this new liability is that Mr Sroubek would have to leave New Zealand upon his release from custody and would be unable to return."
Mr Lees Galloway said the case file provided by INZ when he first made the decision to let Mr Sroubek stay "may not have provided a complete picture".
"The picture painted to me was that his violent offending was in the past, and that his risk of reoffending was low. I did accept there was some risk, which would mean there would have to be conditions in the event that I did allow him to stay in NZ.
"In the end, I did determine there was a potential risk to his safety should he be deported and that the risk he posed to public safety in New Zealand were low.
"I reached those conclusions relying on the information that was presented to me at the time. More information on Mr Sroubek’s travel history and criminal past would have assisted In my decision making."
However, he said the responsibility for the decision was his and that he had apologised to Prime Minister Jacinda Ardern.
It comes after Immigration New Zealand launched an investigation on November 1 into the residency application of Czech drug smuggler Karel Sroubek.
Immigration Minister Iain Lees-Galloway told media at the time he received new information that contradicted that which he used to make his decision to grant residency to Mr Sroubek.
Mr Lees-Galloway said for legal reasons he could not go into details, as it was "important that the investigation is able to occur without any prejudice".
Mr Lees-Galloway wanted a report back "in three weeks, if they can do it sooner than that, then I'd certainly encourage them to do that".
"I have instructed them to make this their top priority."