The stepfather of murdered schoolgirl Karla Cardno has been ordered to leave New Zealand after overstaying for more than 30 years.

Mark Middleton's threats, in media interviews more than 17 years ago, to kill his stepdaughter's murderer appear to have put him in the sight of Immigration New Zealand.

The 60-year-old moved from England with his parents when he was 4 years old in 1962 and hasn't been back since.

But on Tuesday, immigration officers stormed his workplace, accusing him of living here illegally, and put him in a cell at a Wellington police station until Wednesday afternoon.

Middleton described the immigration police as "very, very hostile".

"It was bloody cold for a couple of days, it's quite dehumanising actually."

He said if he was kicked out of the country it would destroy his family as he was the sole breadwinner.

"I've got kids here, my family ... and we face the whole parole thing year after year after year and that hangs like the Sword of Damocles over our heads for four or five months every year."

In 2001, Middleton was sentenced to nine months in prison over threats he made against Paul Joseph Dally, who snatched Karla, 13, from her bike as she rode home from Lower Hutt shops in 1989. Dally raped and tortured Karla for 22 hours before he buried her alive.

But Middleton never served time after the judge suspended the sentenced. His lawyer argued he was suffering from a condition known as chronic hypertrophic grief.

Middleton lives with Karla's mother Veronica in Wellington where, he says, aside from his conviction he had led an uneventful life.

"I've just been keeping my head down," he said.

"I don't go around burgling or stealing ... I've always been a worker, I'm a family man."

Immigration New Zealand assistant general manager Peter Devoy confirmed Middleton was served a deportation order and that he'd been "unlawfully in New Zealand since 23 December 1986".

"Mr Middleton was issued a 30-day visitor visa in November 1986 after he returned to New Zealand from a holiday abroad and did not have valid re-entry permission.

"INZ wrote to Mr Middleton in January 1987 advising him that he needed to regularise his immigration status."

Devoy said Middleton had not made any visa applications since then.

"He came to the attention of INZ last year as his identity was on a pool of unlawful historical clients who could be living in the Wellington area," said Devoy.

"INZ prioritises cases for deportation with those engaged in criminality or who otherwise pose a risk to the integrity of New Zealand's immigration system being the highest priority cases for deportation."

Middleton said the 1986 trip was a family holiday to Fiji.

He said that when he returned to New Zealand, officials queried his passport but let him back in without further questions. He did not recall getting the letter.

"And here we are [four] days ago and they turn up at my work and tell me I'm an overstayer," he said.

Although free from his cell, Middleton isn't free from the deportation order.

He has been granted a two-week reprieve to appeal the decision.

Middleton's lawyer Keith Jefferies said it could all have been sorted out with a phone call.

"It's something where there's been a cock-up 56 years ago which they should have the ability to investigate, remedy and say this has been a bureaucratic mistake.

"I find it an outrage that they've got the power to go and do something like that to somebody.

"And then they say he can't work because he doesn't have a work visa."

Jefferies said being issued a deportation order was serious as it could not be quickly overturned.

He said Immigration New Zealand's investigation needed to stretch back to 1962, when Middleton arrived, not 1986.

"I think the minister has got some responsibility here to rein in his department and say: 'look you're being stupid, this is just ridiculous, you don't do this to people'," he said.

More than 4700 people were deported from New Zealand between 2011 and 2017.

A spokeswoman for Associate Immigration Minister Kris Faafoi said no request for ministerial intervention had been received.

Dally has been in prison for almost 28 years and had been refused parole multiple times.