SARAH FERGUSON, PRESENTER: At a hearing today by the Australian Human Rights Commission into the treatment of children in immigration detention, expert witnesses compelled to give evidence told heart-rending stories: 128 cases of children self-harming, drinking poison and banging their heads against furniture, a 16-year-old boy sexually assaulted in a toilet block, detainees having glasses, hearing aids and medicines confiscated on arrival, a three-year-old girl who started having seizures after her epilepsy medication was taken away from her.

There were gasps in the inquiry when the former director of mental health for the detention centres said the Department of Immigration had instructed them to remove figures of children suffering from mental stress disorders.

Shortly I'll be joined by the president of the Human Rights Commission, Professor Gillian Triggs, but first, here are some of today's witness accounts.

NAOMI SHARP, COUNSEL ASSISTING THE INQUIRY: How would you rate the standard of paediatric care on Christmas Island?

GRANT FERGUSON, GP, CHRISTMAS ISLAND, 2013: Well, I guess there isn't any paediatric care, really, so, very bad.

NAOMI SHARP: How about you, Dr Sanggaran?

JOHN-PAUL SANGGARAN, GP, CHRISTMAS ISLAND, 2013: Abysmal.

GRANT FERGUSON: Kids would arrive very dehydrated, filthy, covered in vomit, human excrement. They would be sleep-deprived, terrified, sunburnt. They were in a pretty bad way.

JOHN-PAUL SANGGARAN: They were not always showered, they were not always fed and watered, they were not always given adequate time for sleep. And in this state, they would then go through an induction process.

KIRSTY DIALLO, CHILD PROTECTION WORKER, NAURU, 2013-'14: There were issues around sanitation. At times the centre actually ran out of soap, so there was no hand soap. And parents expressed concern particularly because there were regular outbreaks of gastro in Nauru.

JOHN-PAUL SANGGARAN: We would run out of some basic things such as IV fluids and speculums and antibiotics, scalpels, things which are required for basic medical care on a daily basis.

NAOMI SHARP: The commission's been provided with some information suggesting that a 16-year-old boy was sexually assaulted by a cleaner on Nauru. Are you able to tell this inquiry anything about that incident?

KIRSTY DIALLO: The 16-year-old boy was near the toilet blocks and there was a male cleaner who was on his own in the centre and it's unclear why he was on his own in the centre 'cause it was against policy. He touched the young - the boy's genitals and then grabbed his own genitals and said, "Jiggy jig."

GRANT FERGUSON: There was a three-year-old girl that arrived to Christmas Island with epilepsy. She was having - she was on two medications when she arrived and her parents brought with her, I believe, medical records and supply of those two medications. They were of course destroyed on arrival, the medications, and the records taken away and not made available to doctors. We didn't stock one of those two medications and she started having seizures. She was just left on that one medication. The doctors were in touch with specialists on the mainland to help manage the patient. Continued to have seizures. Eventually got supply of that medication she initially arrived with, but they'd only ordered a month's worth, and so, in a few weeks' time, they ran out, and so, then they were back to one again. This whole time she was having seizures and they had to try a third medication. And eventually she was transferred off the island after a very long wait, despite many of the doctors asking for her to be transferred off the island. And it's an example of how basically children with complex medical problems just really can't be managed there without appropriate paediatric support.

NAOMI SHARP: Are you aware that some children have tried to poison themselves or ingest harmful substances?

PETER YOUNG, PSYCHIATRIST: Yes.

NAOMI SHARP: Are you aware that some children are banging their heads against walls?

PETER YOUNG: Yeah, that's a common method of self-harm. ... It's quite clear that we've got a large number of children with significant mental distress and disorder in this population.

NAOMI SHARP: What has the department's reaction been to your report?

PETER YOUNG: Sort of reacted with alarm and have asked us to withdraw these figures from our reporting.

NAOMI SHARP: I beg your pardon?

PETER YOUNG: They've asked us to withdraw the figures from our reporting.

MARTIN BOWLES, SECRETARY, IMMIGRATION DEPARTMENT: If in fact there was a problem and some of our staff did an inappropriate thing, I will deal with that. I cannot say that that actually happened in that way. I reject claims made in the media in relation to the conditions on Christmas Island. They have been highly emotive claims which offend greatly the skilled professionals, both public servants and service provider staff, who work to deliver high-quality care in difficult circumstances.