New Zealanders who have committed crimes in Australia are being deported back to their home country after they have served their sentence - and a third have already reoffended upon return.

Almost a third of Kiwi criminals deported from Australia have continued their life of crime here, with some committing violent and sexual offences.

A police briefing to Police Minister Judith Collins in December showed 30 per cent of deportees had come to police attention for reoffending since December 2014.

That was the point when Australia began sending back New Zealand criminals who had done their time, as it tightened its visa cancellation rules.

In the briefing, police told Collins they expected reoffending rates to soar as high as 55 per cent after two years. That was based on their analysis of the first 47 offenders who arrived before Australia's rule-tightening.

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Neither police nor Collins could provide more details on Monday, but police confirmed that 60 deportees from Australia had been charged with 393 offences in the two years between October 2013 and September 2015.

Some deportees had come to police attention for sexual and violent offending, the briefing said.

On average, it took deportees 200 days from their arrival back in New Zealand before they began reoffending.

However, Adam Drollett, a convicted robber deported from Australia, waited only six weeks before robbing banks in Wellington and Auckland.

When he was brought to Wellington District Court in December to face charges, he kicked a Corrections officer and punched a policeman as he vaulted the dock and tried to escape.

Lawyer Chris Nicholls told the court his client had had not lived in New Zealand since he was three.

He returned without being given any information about getting an income, social services, "or any support whatsoever", Nicholls said. "He is stuck with us, and we are stuck with him."

In the weeks before Drollett was jailed, Parliament had rushed to pass laws allowing for a "parole-like" monitoring regime for Kiwis awaiting deportation from Australian detention centres such as Christmas Island.

An information-sharing agreement between the two countries in September also addressed warnings that criminally insane Kiwis had been deported without notice to authorities here.

Collins said the Government was working to support deportees to prevent them reoffending, but noted they had been sent back because of their past.

"We have hundreds of these people coming to New Zealand, and it's of great concern to New Zealanders, and certainly to myself.

"But people forget. There's a lot of talk about them coming back here and being rehabilitated, but they have been deported in most cases for quite serious crimes – not in all cases, but most cases."

Labour MP Kelvin Davis, who took up the cause of Kiwi detainees at Christmas Island, said he was not surprised at the latest figures.

Some deportees were growing desperate when they found barriers to getting jobs, or landing in communities where they had no family.

"Prior to the law change last year, they were being dumped and there was no support for them."

Both MPs said they expected to see reoffending rates reduce under the new monitoring regime.

Collins said she had recently been told deportees had been co-operating with the new regime, with most agreeing for their fingerprints to be taken on arrival.

Police Association president Greg O'Connor added that, anecdotally, police in New Zealand were finding their Australian counterparts had become more prompt at providing background on deported offenders.

At the time the new law was passed, Justice Minister Amy Adams said the Government could not promise that overseas offenders returning to New Zealand would not reoffend – but monitoring them would help authorities manage their risk.

On Monday, Adams said the latest police figures were in line with New Zealand prisoners' general reoffending rates.

BY THE NUMBERS

* A total of 299 returning offenders (282 from Australia) have arrived in New Zealand between December 10, 2014, and January 31, 2016

* Before Australia's rule-tightening in December 2014, 47 offenders were returned to New Zealand

* Of those, 26 were charged within two years of returning. They were charged with 243 offences between them

* Between December 2014 and September 2015, 173 offenders were deported to New Zealand

* 34 of those have been charged with offences since returning, as at October 2015. They were charged with 150 offences between them

Source: NZ Police