The deputy chief executive of Immigration New Zealand says the information Iain Lees-Galloway labelled as new was "in the original file" and wasn't "specifically relevant to the decision" to grant Karel Sroubek residency.

The Czech drug smuggler is now liable for deportation after an Immigration NZ review.

Iain Lees-Galloway told Mike Hosking this morning, he changed his decision after "new" information was revealed in the Immigration New Zealand review.

However deputy chief executive Greg Patchell told Mike Hosking the information Lees-Galloway was referring to was actually in the original file but it wasn't "relevant to the decision".

"That summary information was in the original file [but] that information wasn't specifically relevant to the decision he was asked to make the first time around. The minister sub-sequentially asked us to do some additional work and we have got more information from the courts and the Czech Republic."

When asked whether he thought Lees-Galloway made the right decision, Patchell said he can't comment. 

"Regrettably I can't answer that question. It's a discretion decision for the minister and the minister alone."

However, he said Lees-Galloway isn't required to read files before making decisions because he has absolute discretion.

"He doesn't even have to look at the file actually in terms of considering the request. If he does he needs to consider the file, consider all the balancing information in it and make a decision as an independent decision maker."

He said the information they got from the court showed Karel Sroubek was "present when he was convicted".

The deputy chief executive said the reason Sroubek's trip back to the Czech Republic wasn't included in the file was because it would be seen to be prejudicial.

Case history

Lees-Galloway had cancelled Sroubek's deportation liability in September and granted him residency in his real name, even though Sroubek had gang associations and is in prison for smuggling MDMA.

Earlier this month, the minister ordered a review of the decision after a court document noted that Sroubek twice travelled to Europe in 2009, which potentially contradicted the reasons why he was granted residency in the first place.

Sroubek's case has dominated political headlines this month as the National Party has called for Lees-Galloway to be sacked for what they say was an incompetent decision.

Lees-Galloway came under intense pressure after he conceded that he made the decision on Sroubek in 45 minutes and did not read the entire case file.

Prime Minister Jacinda Ardern has stood by her minister throughout the saga, expressing full confidence in him and saying that the process around these cases needed to be improved.

Immigration NZ investigated the case in the previous weeks and handed the case back to the minister at the start of this week.

National MPs have used Question Time this month to reveal that a house that Sroubek claimed a financial interest in was allegedly burgled, that Sroubek had allegedly made threatening phone calls to his estranged wife, and that a man and his family were put into a witness protection programme due to alleged actions by Sroubek - in a court case where he was acquitted.

Sroubek released a statement saying he had nothing to do with the alleged burglary, and that the key witness in the trial that involved the witness protection programme was discredited.

Sroubek's mother Mila Sroubkova has came out in support of her son, telling Radio NZ's Checkpoint that her son was not a gangster and pleading to Lees-Galloway to give her son one final chance.

She also confirmed that Sroubek travelled to the Czech Republic in 2009 for one night, leaving after his family told him to go for his own safety.

Timeline

2003: Karel Sroubek flees Czech Republic as witness to a murder. Enters New Zealand with false passport in name of Jan Antolik. Later gains residency and represents his new country as a kickboxer.

2009: True identity discovered when Cz...