Prime Minister Jacinda Ardern says three weeks was too long for the investigation into the New Zealand residency of a Czech drug smuggler.

The investigation into the New Zealand residency of a Czech drug smuggler hasn't been good enough, Prime Minister Jacinda Ardern says.

Ardern made the comments while addressing the media in Dunedin on Friday, ahead of her first Labour annual conference speech as the party's leader this weekend.

Her Immigration Minister Iain Lees-Galloway has come under fire for granting residency to Czech national Karel Sroubek - a convicted drug smuggler, immigration fraudster and known gang associate wanted in the Czech Republic for allegedly injuring a police officer.

HAMISH MCNEILLY/STUFF Prime Minister Jacinda Ardern on convicted drug smuggler Karel Sroubek.

There were reports the Czech republic would request his extradition. But a spokesman for Justice Minister Andrew Little said no formal request had been received by New Zealand.

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Ardern said three weeks was too long for the investigation, and she wanted answers "as quickly as possible".

STACEY KIRK/STUFF Immigration Minister Iain Lees-Galloway announces inquiry into Czech criminal residency decision.

"My expectation is that it is done very quickly, because from what I've seen this hasn't been good enough."

If it was found Immigration NZ was not passing on the relevant information to the minister "we would absolutely need to rectify that, and to get to the bottom of that".

"But for me, it is about resolving this particular issue and then see if there was a systemic issue at play."

CARMEN BIRD Kickboxer Jan Antolik, whose real name is Karel Sroubek, is a Czech national who was jailed for importing MDMA into New Zealand. While in prison, Immigration Minister Iain Lees-Galloway granted him permanent residency.

The minister could only deal with the information before him, Ardern said.

'It seems clear on the face of it that there is some contradictory information."

She had spoken with the minister, and the expectation was the information had to reviewed quickly, within three weeks. His information contradicted with what was in the public domain, and she said the minister had gone back to his department to reconcile those differences.

She rejected any suggestion officials were thrown under a bus. "This is about making sure we have a system in place that is working".

Ardern is due to address the Labour Party conference at Dunedin Town Hall on Sunday afternoon.

The conference is scheduled to start on Saturday.