Czech national Karel Sroubek, also known as Jan Antolik, was granted permanent residency, despite being in prison for importing MDMA.

Immigration New Zealand has confirmed the case file used to grant Karel Sroubek residency was hundreds of pages long, with a 12 page summary, and did not include documentation showing the Czech drug smuggler had returned to Europe.

It has also since received information from Czech authorities and expects to complete its investigation into the case next week.

On Thursday it was revealed Immigration Minister Iain Lees-Galloway made the residency decision in less than an hour and he did not read the full file.

WARWICK SMITH/STUFF Immigration Minister Iain Lees-Galloway made the decision to grant Sroubek residency in less than an hour and without reading the full file.

The minister said he had read "aspects" of the file.

Immigration New Zealand (INZ) general manager Stephen Dunstan confirmed on Friday the Sroubek file was "several hundred" pages long, with sentencing judges' notes appended to it.

The "really good summary" in the case file was was about 12 pages long, he said.

The construction of files going to the minister had been done the same way for 15 years, he said.

The standard practice included reasons why the person was liable, the person's immigration history, details about any convictions, the client's personal circumstances and any comments they wanted to make, which were sometimes quite extensive, he said.

SUPPLIED Immigration New Zealand's general manager Stephen Dunstan confirmed on Friday the Sroubek file was “several hundred” pages long, with sentencing judges’ notes appended to it. The summary was about 12 pages.

Sroubek's file would have included details of his convictions that included the judge's sentencing notes.

Dunstan suggested the file did not contain documents that showed Sroubek returned to Europe.

When asked if the minister had the documentation that showed Sroubek had returned to Europe, he said: "That wasn't in the file - I don't want to get into the file too much because obviously there is an investigation underway".

ROSA WOODS & ALEX LIU/STUFF Prime Minister Jacinda Ardern defended her minister in November 2018 over the Karel Sroubek decision.

When asked if the file contained information about what Sroubek got up to in the Czech Republic, he said immigration did not usually provide that information.

The information would be based on a particular conviction that made him liable for deportation.

If information was missing then it was not relevant to a decision a minister was going to make or immigration did not hold it, he said.

KEVIN STENT/STUFF National’s immigration spokesman Michael Woodhouse has boiled the decision down to two scenarios - a complete “cock-up” or political pressures being applied.

During sitting weeks the minister would have one day to look at "quite large" case files and often there were between two and five put before the minister at any one time, he said.

Stuff asked Lees-Galloway's office how many files he looked at on the day he made the Sroubek decision but was told that information could not yet be provided.

Senior officials, familiar with all the material, would also have been in the room with the minister to his answer questions, Dunstan said.

Immigration officials ran a robust process gathering information for a minister and did not run investigations, he said.

No recommendations were included. "That is at the absolute discretion of the decision maker," he said.

Last week Lees-Galloway ordered a review of the case when information came to light that "directly contradicted" what he relied upon when making his decision.

INZ had gone back to the Czech authorities as part of its investigation and got some information from them, which was being looked at, Dunstan said.

The Investigation undertaken by INZ's compliance team was making good progress and he was hopeful it would be completed next week.

But any findings would also need to be provided to Sroubek to ensure the process was "squeaky clean", he said.

It is understood the investigation was examining new allegations that Sroubek had already been back to the Czech Republic, and his ex-wife no longer supported in his application.

National's immigration spokesman Michael Woodhouse said when he was minister he would meet with officials once a house sitting session and there might be between two and five files in the batch to consider and he would also be given an oral report.

The reading of the summary notes wasn't unusual or a bad thing if the trajectory of the prima facie case (made by officials) for deportation was going to be followed, he said.

The start point was that they were liable for deportation and then he would consider options.

Difficult cases came to him on numerous occasions before he signed them off.

"I'm trying to picture that file in my head. On the facts as we know it, I can not understand why he made the decision he did."

He boiled it down to two scenarios - it was a complete "cock-up" and terrible decision from a minister not over his portfolio, which he doubted.

"But I think there may have been representations made or political pressures applied."

Lees-Galloway has remained tight lipped on why he made the decision to grant residency to Sroubek, citing the ongoing investigation.

He has maintained the decision was based on all the information presented to him.