The Immigration NZ case file on Karel Sroubek did not include information that he may have travelled to the Czech Republic in 2009, but it is unclear if that is enough for the minister to reverse his residency decision.

Prime Minister Jacinda Ardern continues to stand by Immigration Minister Iain Lees-Galloway, even though he admitted making his decision in about an hour and without reading the whole case file.

Immigration NZ is reviewing the Sroubek case after contradictory information emerged that, if proven, would undermine Lees-Galloway's original decision to cancel Sroubek's deportation liability.

The Czech Republic wants Sroubek to face charges in his native country, but is waiting for Immigration NZ to complete its investigation.

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"The extradition process has not begun," said Czech Consul General Hana Flanderova in the Sydney office, which represents the Czech Republic in New Zealand.

"The Czech Republic is keen on getting Mr Sroubek to the Czech Republic (either through the deportation or extradition) and is awaiting the final information from the New Zealand authorities about the deportation order of Mr Sroubek."

Ardern and Lees-Galloway have declined to talk about the detail of the contradictory information, though Ardern has asked people to read between the lines.

But Labour MP Michael Wood revealed it was the suggestion that Sroubek had returned to the Czech Republic in 2009, which was contained in publicly-available court documents.

"What's come through in the media is the suggestion that Mr Sroubek may have gone back to the Czech Republic. If that is indeed the case, that would be contradictory to the information that the Minister was provided by his department," Wood told the AM Show.

"My understanding is that wasn't in the file at all."

It could be argued that Sroubek's life might still be in danger if he were deported in spite of the 2009 trips, but Queen City Law immigration lawyer Jack Cheng said that would be a hard sell.

"It's highly contradictory. If your life is truly in danger for some reason, you just wouldn't go back. If you did, it would be hard to reconcile that with your life being in real danger.

"I think they're scrambling to find a way to get this guy out, but the decision has to be watertight, otherwise Sroubek will challenge it and the drama will just drag on."

Cheng said if the minister reversed his position but didn't base it on new information, Sroubek could seek a judicial review.

Even if the information wasn't in the original case file but was available in a public court document, Cheng said Sroubek might still challenge it.

"On that basis it was readily accessible to Immigration NZ, so they should have been aware of it and you could argue that it's technically not new information."

Ardern continued to defend Lees-Galloway this morning, saying he was only following the process that had been in place for successive ministers.

"I'm not saying that I'm happy with this process or with this outcome. Obviously I'm not happy with this situation," she told Newstalk ZB.

"This is not unique to our Immigration Minister. Successive immigration ministers have gone through a process with Immigration [NZ] that I think can be improved."

The National Party is calling on Lees-Galloway to resign, saying he has no credibility left.

"The Prime Minister cannot expect the public to have confidence in any of his decisions, given his careless approach to Sroubek's residency," National leader Simon Bridges said.

Asked if she would accept Lees-Galloway's resignation, Ardern said: "No, because at the moment what I'm focused on is getting this issue right."