The Government has ordered an independent review into its practice of detaining asylum seekers in prison, a move that advocacy groups and lawyers have been calling for for years.

Associate Immigration Minister Phil Twyford announced this morning the review is in response to a recent damning report into asylum seekers' treatment in prison, and the work of Amnesty International and the Asylum Seekers Support Trust.

"We want to ensure treatment of asylum seekers is consistent with our human rights obligations under international law," Twyford posted to social media.

The confronting Amnesty report and Herald investigation in May revealed the atrocities people seeking asylum in New Zealand experienced during their time in prison.

Allegations of rape, physical and verbal abuse emerged from some 86 detained asylum seekers in the past five years. One man had to remain in prison for three years while a decision was being made on his application to live in New Zealand.

Three people seeking asylum, who were detained at the time of the Herald's investigation in May, described being bullied by their cellmates, being unable to contact family members and "feeling low expectations of success" due to their treatment by Immigration New Zealand.

Others in the Amnesty report spoke of being physically assaulted by other prisoners to the point their bones were broken, feeling forced into prison "fight clubs" and feeling violated during strip searches.

Asylum Seekers Support Trust general manager Tim Maurice said he's very excited about the independent review, which will be led by Victoria Casey QC.

"It means so much for our clients," he told the Herald.

"The guy that was locked up for 18 months while his wife had a baby, people like that.

"They guy that was locked up for three years, letting them know that there's somebody who is trying to stop this from happening to anybody else in the future ... [I'm] thinking of them."

The review will focus on a selection of detention decisions from the last five years, and the "operational manual" to check it fits with human rights obligations, Maurice said.

"They haven't said they will stop using prison. They said they will continue to use [it] while the review is being done, which is disappointing.

"We want them to stop using it now. They know it's not right.

"But it's definitely a huge step in the right direction."

Maurice hopes the Government won't "cherry-pick the cases to investigate to "make them look better".

Amnesty International spokeswoman Meg de Ronde said seeing ministers willing to recognise that there is an issue, gives her hope.

"There are many people living in community in New Zealand who weren't in the report ... who will have been held at Mt Eden or one of our other criminal facilities.

"This is for them, that they're going to start to see movement and review of this practice."

But she said the review does not mean the problem has been solved.

"There is work to do to make sure criminal facilities are not seen as viable by this Government."

Amnesty met with ministers in June and have been working with them about what the scope of the review could include, de Ronde said.

"We will keep the pressure up to make sure the Government follows through and stops using prisons to hold people in this way."

The Government is aiming to have the review finished by the end of the year.