Almost half of those who've been deported to NZ, from Australia, have reoffended.

Almost half the criminals deported to New Zealand from Australia have reoffended.

Police Commissioner Mike Bush said 44 per cent of those who had been forced to return to New Zealand, after being criminally convicted in Australia, had reoffended.

In December last year, a quarter of the 1023 deportees forced out of Australia in the past two years had reoffended.

MATT DUNCAN / FAIRFAX NZ. Police Commissioner Mike Bush says if the deportees haven't already reoffended, then they will, without intervention.

During a select committee hearing on Thursday, Bush said the proportion of those who had reoffended since returning to New Zealand shores had increased to 44 per cent.

READ MORE:

* 'Terrifying' offender deported to NZ, despite living in Australia since he was 1 year old

* Only those with genuine NZ links should be deported from Australia, PM says

* Kiwis biggest group held in Australian detention centres

He then added: "If they haven't [already offended], they will."

"We anticipate that, so we're keeping a very close eye."

Police knew who the deportees were, and knew their criminal history, so as best they could - within the confines of the law - police were keeping an eye on the deportees.

Officers had also made an effort to open communication channels with the offenders as early as possible after their return to New Zealand. This helped authorities monitor what they were doing, he said.

Bush said he did not know how many of those offenders were serving prison sentences.

Justice select committee member and Labour MP Greg O'Connor asked Bush whether the deportees were adding to organised crime, and gang-related crime in New Zealand.

O'Connor also asked whether the arrival of the deportees had anything to do with the establishment of a New Zealand chapter of the dangerous Australian biker gang the Comancheros.

Bush said he was unsure of the deportees' gang links.

Last year, Ardern said only those with genuine links to the country should be deported to New Zealand.

Some of the deportees had a string of criminal convictions but had no further link to New Zealand than citizenship.

Alex Viane, 40, was born in American Samoa and became a New Zealand citizen as a child, but never entered the country.

Meanwhile, a man with more than 200 criminal convictions is being deported to New Zealand, despite not having lived in New Zealand since he was a toddler.

Jacob Symonds, who is in his 30s, moved to Australia with his adoptive parents when he was 1 year old but never got citizenship.