Immigration Minister Scott Morrison needs to come clean about the conditions in off-shore detention, the president of the Human Rights Commission says.

Speaking outside the Human Rights Commission Inquiry into Children in Detention in Sydney on Thursday, Professor Gillian Triggs said Australia needs to ask whether it’s gone too far amid testimony about the cruel conditions at facilities on Christmas Island and Nauru.

“The inhumanity, the cruelty of these processes is very apparent and when it’s repeated without any conditions attached by all of these medical experts, as Australians we have to ask have we gone too far?” she told journalists.

Psychiatrist Peter Young, who is a former mental health services director with the International Health and Medical Service (IHMS), told the commission that there were elements of a cover-up with the immigration department wanting the extent of mental health problems among children removed from official reports.

“This is extremely worrying,” Prof Triggs said.

“The minister has a responsibility to be much more transparent about what is happening.

“We’re trying to get facts right when frankly it would be much simpler for the minister to provide the Australian public with this information in the first instance.”

Other medical experts told of how personal possessions are stripped from detainees, causing medical complications for some.

A three-year-old girl with epilepsy ended up having seizures after detention staff took away her medication and then faced long delays in getting one of the two drugs she needed.

On Thursday morning, the commission heard from four doctors who had worked in or visited detention centres on Nauru and Christmas Island.

Sydney University Pediatrics Professor Elizabeth Elliott said a lack of access to the full spectrum of medical care made Christmas Island an inappropriate place to hold children with special medical needs.

She described the effects of extended detention on a family of four: the mother self harmed, a young infant stopped putting on weight and a 12-year-old girl spent three days with her head under a blanket and told doctors she wanted to die.

Her 13-year-old brother developed a stutter and began to exhibit other signs of anxiety.

Dr Elliott said there was a lack of compassion in the detention process that needs to be dealt with.

“Regardless of the political policy, these people are currently in our care and we must treat them humanely and we must offer them, particularly the children, the access to health and education and freedom that we expect for any of our children,” Prof Elliott said.

The numbers

Australia is holding 659 children in immigration detention, the human rights commission has heard.

Department of Immigration and Border Protection secretary Martin Bowles told a national inquiry the number of children being held in detention centres in Australia and offshore had fallen by more than 1330 since hitting a peak of 1992 in July, 2013.

Mr Bowles said the number of children being held at the Christmas Island detention centre was now 153, down by more than 530 in the past year.

Some of those children had been transferred to Nauru, where there were now 185 children being held.

Prof Triggs asked Mr Bowles if he was being “straight forward with the Australian public” in stating numbers on Christmas Island were being reduced if children had simply been transferred to Nauru.

Mr Bowles responded that there had been a “significant and considerable decrease” in numbers of children being held.

“I reject the imputation that we are either misleading or lying to anybody in relation to the reduction of children in detention,” he told the inquiry in Sydney on Thursday.

The commission heard there are about 37 children among the 157 Sri Lankan asylum seekers recently transferred to the Curtin detention centre in Western Australia.

Counsel assisting the inquiry Naomi Sharp asked Mr Bowles if he could confirm there were babies among those children.

Mr Bowles that he could not confirm there were babies without having confirmed the “biodata” from assessment of the group, but said there were small children.

In a statement to the inquiry Mr Bowles rejected claims made in the media about poor health care standards at the Christmas Island detention centre, saying the claims “offend greatly” staff working at the centre.

Mr Bowles said healthcare services on Christmas Island were “commensurate with those available to the Australian community”.

Mr Bowles said he would make no comments on Nauru as the scope of the commission extended only to onshore detention centres.

The AHRC national inquiry into the health and well-being of children in immigration detention continues.