Church leaders have described Australia's treatment of unaccompanied children seeking asylum as a "sick joke".
In a report titled Protecting The Lonely Children, the Australian Churches Refugee Taskforce says there is state-sanctioned child abuse in onshore and offshore detention facilities.
Immigration Minister Scott Morrison has flatly rejected the claims, but the taskforce is calling for him to be stripped of his guardianship role of children in immigration detention.
The report's author, Reverend Dr Peter Catt, says their treatment amounts to child abuse.
"The Government knows that it's detrimental to the health and wellbeing of the children and is doing nothing about it," he said.
"In years to come, people will look back and go, 'well that's child abuse'."
The task comprises nine Christian denominations. Its chief executive, Misha Coleman, says the responsibility to care for children is at odds with keeping them in detention.
"We're definitely not singling out this minister, but the way the Act stands in Australia at the moment, the minister for immigration is both the guardian, so the de facto parent, as well as being the jailer, the juror, and the person who determines whether they're sent offshore or not," she said.
"That doesn't happen in other jurisdictions. That's quite an anomaly in the Australian legislative framework.
"So we are not the first organisation to call for there to be an independent statutory guardian that is resourced to have the best interests of the child at heart."
Ms Coleman says the system needs to be reviewed and overhauled.
"We will never again stand by and do nothing about child abuse," she said.
"We haven't done primary research in the centres but we have relied on people who visit the centres often and we've relied on a whole range of credible reports, UN committee reports, and we do have a number of letters that we've received directly from children themselves.
"Children in our detention facilities are suffering everything from untreated sexual infections to tuberculosis. We've got children on Christmas Island, you've got rotting teeth, fungal infections.
"They're biting themselves, they're banging their heads into furniture due to their appalling state of mental health."
Mr Morrison has not seen the report but says claims of state-sanctioned abuse are shocking and offensive.
He says he takes his guardianship responsibilities seriously and that the Government is committed to ensuring children are protected from exploitation and abuse.