Immigration NZ has completed an investigation into whether Kim Dotcom can be deported from New Zealand for failing to declare a dangerous driving conviction - but it's refusing to say what the outcome is.

The department has not even told its new minister, Iain Lees-Galloway, the inquiry is complete although legal experts say it almost certainly would recommend Dotcom be deported.

But that won't happen without the report going to Lees-Galloway - it's his job to make the decision.

Immigration NZ won't say what the outcome is and instead aims to wait for the end of the legal fight to extradite Dotcom to the United States to stand trial for alleged copyright breaches.

The NZ Herald broke the story that led to the investigation in 2014, revealing Dotcom applied for residency without declaring a dangerous driving conviction from 2009.

Court records show he was clocked doing 149km/h in a 50km/h zone.

There was no mention of the conviction in his residency application eight months later, which asked: "Have you or your family members included in your application ever been convicted of an offence (including a traffic offence) committed in the last five years involving dangerous driving?"

Dotcom's application showed the box marked "no" had been checked.

Kim Dotcom with former wife Mona Dotcom and family in 2012 - all are under deportation scrutiny by Immigration NZ. (Photo / Michael Craig)

Immigration NZ's resolutions manager Margaret Cantlon said "any question" of Dotcom's deportation would not go to Lees-Galloway until the extradition proceedings, including appeals and any judicial review, were finished.

"INZ has not briefed the new minister on the deportation case."

Asked if the length of the inquiry was a record, she said there were no "statistics in a reportable format on the length of time it takes to deal with cases involving potential liability for deportation".

Kim Dotcom with former wife Mona - the pair were travelling together when Dotcom was clocked doing 149km/h in a 50km/h zone in 2009. (Photo / NZ Herald)

A spokesman for Lees-Galloway confirmed the minister had had no briefings on Dotcom.

"The minister has received no information on this issue to date."

The inquiry into Dotcom has the potential to affect his whole family, as former wife Mona and five children came into New Zealand on his residency. He has since remarried, wedding Elizabeth Donnelly last month.

He entered the country on a special scheme intended to attract wealthy foreigners, giving three-years residency and a fast-track to citizenship to those who invested $10m or more in New Zealand.

Dotcom has called deportation the government's "plan B" if efforts to extradite him to the United States fail.

But he has said that effort to remove him would result in another fight through the courts.

Dotcom said he believed Immigration would "sit on it" because Labour's Lees-Galloway "would not deport my family for a speeding ticket".

"I'm not concerned about this stillborn plan by the former National government. They thought if extradition fails, which it will, they can just deport me."

Minister of Immigration Iain Lees-Galloway has not been briefed on his department's inquiry into deporting Kim Dotcom. (Photo / Brett Phibbs)

He predicted deportation would fail, saying it had been studied and "resulted in a good laugh by my legal team".

If deported, Dotcom would likely be sent back to Germany, which would pose a problem for the United States because it has different extradition rules.

Germany has already refused to extradite one of the Megaupload accused within its borders.

It's not the first time Dotcom has faced scrutiny over his residency application.

In 2010, when Dotcom was granted residency, his lawyers had to tell Immigration NZ within days of his arrival in the country that share trading convictions in Hong Kong had not been declared.

In that case, the lawyers explained that Dotcom was unable to disclose the charges because of Hong Kong law.

Kim and Liz Dotcom, who were married earlier this year. Photo / Supplied

On that occasion, Immigration NZ sent its inquiry report to then-Immigration Minister Jonathan Coleman, who said it was fine for Dotcom to stay. The whole process took about two months, including Christmas.

Lane Neave law firm partner Mark Williams said the final decision was down to Lees-Galloway and "the minister is going to hope extradition does the job for him".

It would save carrying out unnecessary work, potentially fighting through the court and save the minister from a political hot potato.

"My view is if it got to the position where the minister was looking at this under a National government, it would be a practical certainty he would be deported."

Under the new government, he said it still looked a "slam dunk" because it was the second time a new conviction had emerged. "That would not be viewed favourably at all."

Williams, who is considered an international expert on immigration law, holds roles at leading universities and sits on the NZ Law Society immigration committee, said the international perception of New Zealand's immigration system was important.

"You'd almost have to deport someone like that to send a message."

Williams said appeals were heard by the Immigration and Protection Tribunal and could be subject to judicial review at the High Court. Successful appeals beyond the High Court were rare.

The Megaupload accused - Bram Van der Kolk, Kim Dotcom, Mathias Ortmann and Finn Batato.

He said Immigration NZ's position was "practical" because if Dotcom was extradited and then imprisoned in the US there would be no need to go through the deportation process.

Simon Laurent of Laurent Law, who also sits on the New Zealand Law Society immigration committee, said Dotcom would have to show there was no deliberate attempt to conceal the conviction.

But he also said it was ultimately up to the minister. "Concealment is one of those things they lay into people very heavily for."

Laurent, who has had leading roles across immigration law and with the NZ Association of Migration and Investment, said the longer decisions took created greater reasons for continuing to stay in New Zealand.

He said delays were not unusual and cases could linger, with the extra time creating stronger ties between the focus of a deportation order and New Zealand.

National Party immigration spokesman Simon Bridges said "there should be no special treatment for Kim Dotcom".

He said he would expect Immigration NZ was taking the same approach it would to anyone facing deportation.

Kim Dotcom has said he is confident Labour's new Minister of Immigration, Iain Lees-Galloway, will not deport him and his family. Photo / Michael Craig

Immigration NZ granted Dotcom's residency application despite being told by the NZ Security Intelligence Service that the FBI was investigating.

Documents obtained by the Herald through the OIA showed NZSIS staff tried to block the residency application but dropped its objection after being told there was "political pressure" to let the tycoon into New Zealand.

At the time, the new residency scheme was having little success and - documents show - Coleman was eager to get "high rollers" into the country.

The case of Dotcom and the three others facing extradition with him is before the Court of Appeal in Wellington.

Although Dotcom is charged with criminal copyright violation in the US, the High Court ruled there was no such crime in New Zealand. It instead accepted the US argument that Dotcom should be extradited on "fraud".

The shift from copyright to fraud is the main basis of the appeals. Both sides have said they intend to appeal the outcome to the Supreme Court.

Deportation and extradition - what's the difference?

Deportation:

It is the act of expelling someone from a country, usually back to the country of their citizenship. In the case of people with residency in New Zealand, they have gone through a process that has resulted in losing their legal right to stay. They are then served a deportation order signed by the Minister of Immigration.

Extradition: It is the act of allowing a foreign nation to take someone from New Zealand to face criminal charges in that foreign country. The right to do so exists under agreements made between countries. In New Zealand, extradition hearings take place in the district court, which establishes if there is a case to answer. The Minister of Justice then signs the extradition order.