A letter from 15 doctors documenting medical neglect of asylum seekers detained on Christmas Island has been “largely ignored”, one its co-signatories has said.



Speaking at the University of New South Wales on Tuesday evening, Dr John-Paul Sanggaran said IHMS, the private medical provider in Australia’s detention centres, had offered only a single-page letter in response to the 92-page document revealed by Guardian Australian in December, which is the most forensic and comprehensive portrait of the state of medical care in detention that has been published.



Guardian Australia exclusively reported the contents of the letter, which recorded the “numerous unsafe practices and gross departures from generally accepted medical standards which have posed significant risk to patients and caused considerable harm” on Christmas Island.



The immigration minister, Scott Morrison, repeatedly declined to answer questions on the letter, stating in December he was “appropriately assessing the claims that have been made”.



Sanggaran said in his address: “Despite over 18,000 words of detailed concerns there has been no adequate response. There is a single page we have received from IHMS and I got to see a demo version of their new IT system.



“There are many individuals for which I have ongoing concern. I do not know how they have progressed. Unfortunately, due to my experience working in that system, I do not have confidence that they somehow now receive appropriate care.”



The letter articulated in detail widespread flaws in the health assessment process. It said some asylum seekers were seen by a doctor for less than five minutes before being approved for offshore transfer, under the Coalition government’s “unsafe” target of sending asylum seekers abroad after just 48 hours. Flaws in the antenatal and paediatric provision, the prescription process, and delays in providing urgent medical help were also set out in the letter, which said doctors on Christmas Island were being “paid to accept risk”.



In response to Sanggaran’s comments on Tuesday, a spokeswoman for IHMS said the organisation had taken the letter “most seriously”.



“Our senior medical staff discussed the contents at length in person and by telephone with Dr Sanggaran and other authors throughout December and January. We conducted a full review of the recommendations and discussed this with the Department of Immigration and Border Protection.”



IHMS declined to detail the nature and contents of the review and Morrison did not respond to a request for comment.



Sanggaran’s speech ran through many of the details articulated in the letter. In the case of Latifa, the pregnant woman transferred to Nauru to “set an example”, Sanggaran said medical staff on Christmas Island believed Latifa was carrying twins before it was revealed on Nauru she was not.



“We would have known that she was carrying a singleton pregnancy if basic standards of antenatal care had been met,” Sanggaran said.



“We have the capacity to provide adequate care to this vulnerable population and we have the ethical responsibility to do so. To continue in this manner is a disgrace, and shameful to all those that call themselves Australian.”