A New Zealand national claims his head was smashed into a glass window by Perth prison guards while he was detained without charge for several months for links to a motorcycle gang.

Ko Haapu, who was detained in Casuarina maximum security prison after his visa was revoked, says he still had the scars on his face from the assault.

"They would just keep pushing and pushing and trying to get us to break, so when I started refusing to be part of their system as a prisoner, my wrists were locked and my head was smashed into the glass windows," Mr Haapu told Radio New Zealand on Thursday.

"They made sure to lock my door and push everyone out of those rooms before they let me out so there were no witnesses there."

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Mr Haapu's detention drew fire from across the ditch in early November when New Zealand Maori Party co-leader Marama Fox suggested the 34-year-old's imprisonment was a breach of human rights.

Australian justice minister Michael Keenan justified the imprisonment of Mr Haapu - an Afghanistan war veteran - by saying there was credible evidence he was abusing the privilege of his Australian visa by joining the Rebels motorcycle gang.

Mr Keenan said at the time he was comfortable with detaining and deporting a non-Australian who hadn't been officially charged with a criminal offence.

"I'm very comfortable with that because it is very difficult to secure convictions in Australia - there's a very high threshold for us to gather the evidence and prosecute people," Mr Keenan told 6PR.

Mr Haapu, a former New Zealand Army lance corporal, earned three medals of honour and was part of the gun battle in which Lieutenant Timothy O'Donnell was killed in 2010.

He was also part of New Zealand Prime Minister John Key's security detail when he visited troops in Kabul and Bamiyan.

Mr Haapu said he was forced to be imprisoned with WA's worst criminal offenders in Casuarina Prison, despite never being charged.

"Detainees were mixed in with the worst of the worst - Casuarina is not a playground - you've got the worst serial rapists there, you've got the worst serial pedophiles there, you've got the worst murderers, yet we were all amongst it."

In the interview, Mr Haapu was asked what he would say to Australian immigration minister Peter Dutton if he had the chance.

"Is it the colour of my skin that you're afraid of or is it the people we are - proud people - that come to your country to do better, is that what you're afraid of?"

- AAP