The review of Czech drug-smuggler Karel Sroubek's residency case will be delayed further after Immigration New Zealand granted Mr Sroubek an extension.

Photo: RNZ / Carmen Bird Photography

Immigration Minister Iain Lees-Galloway has been under intense political pressure over his decision not to deport Sroubek, and ordered a review after conflicting information arose.

The original deadline for Mr Sroubek's response to the investigation was next Wednesday, 21 November, marking a three-week deadline.

Prime Minister Jacinda Ardern and Mr Lees-Galloway both previously indicated that was already too long for their liking.

National leader Simon Bridges says the extension shows utter incompetence by this government.

He said it shattered the promises made by Immigration Minister Iain Lees-Galloway, Prime Minister Jacinda Ardern and deputy Prime Minister Winston Peters, who all said they'd make quick work of this review.

"The prime minister said to New Zealanders 'don't judge me on the actual decision, judge me on the way we fix it.' Well, I think New Zealanders will be judging her right now," Mr Bridges said.

He said the original decision lacked due diligence, and it had only been a shambles since.

"When they were going through what was clearly a bad decision and looking at a process around it, they should've then taken some time to work out what would be a timeline, what would be legally the right thing to do.

"They clearly didn't do that, they're working more by guess and by hope than any sort of good, competent process."

The new extension granted to Mr Sroubek's legal team pushes the deadline out to at least a month.