The Department of Immigration directed staff working in the Nauru immigration detention centre not to make submissions to a Human Rights Commission inquiry, a senate committee has heard.

Dr Peter Young, who formerly served as the director of mental health services at detention health contractor International Health Medical Services (IHMS), told the Senate it was made clear to staff working in immigration detention they should not speak out about what they were seeing.

“A particular example occurred with the Human Rights Commission inquiry,” Dr Young said.

“When there were submissions made to the inquiry, the Department – I recall saying – that people should be warned not to make submissions and that if they made submissions… they would find out who they were and take action.”

Dr Young said the warning was conveyed at a meeting involving IHMS and Department staff from Canberra, but could not recall exactly who was in the meeting.

“I was taken aback that [this]was the sort of attitude that would be taken,” he said.

“I thought that was, again, displaying this very obsessive need to try and keep everything under secrecy and control and interfering with the proper processes of the inquiry.”

The Human Rights Commission was prevented from including Nauru in its inquiry but still received anonymous submissions from staff working in the centre, detailing allegations of sexual assault.

Despite the fact the allegations were later investigated in the Moss Review and found to be credible, the Department of Immigration asked the Australian Federal Police to investigate the person who made the anonymous submission.

After its report was released, Coalition Ministers denounced Commission President Gillian Triggs, an attack which gained new impetus this week after Triggs was accused of linking the executions of Andrew Chan and Myuran Sukumaran to Australia’s poor relationship with Indonesia on asylum seeker issues.

Dr Young’s appearance before the Senate committee today was part of an ongoing inquiry into the processing of asylum seekers on Nauru, a cornerstone of the bipartisan backed policy of offshore detention, processing, and settlement.

Dr Young also told the committee that the Nauruan hospital had “botched” surgery on an asylum seeker, and that the Department of Immigration had been reluctant to report the incident.

“There was basically a surgical report that showed the surgery had been performed incompetently… [the Department]were very reluctant to do anything about it,” he said.

Since then, further instances of poor practice at the Nauruan hospital have been alleged.

In the most recent case, an 11-year-old refugee was left with a potentially permanent impairment after being misdiagnosed at the hospital.

Action was only taken after doctors in Australia got hold of the boy’s x-rays and circulated them to specialists, who confirmed he needed surgery. It forced the Nauruan government to request Australia send a medical team to the island.

Dr Young said that while he worked for IHMS, staff had raised concerns about the hospital but been told by the Department to continue referring asylum seekers there. He said the Department had been hesitant to agree to evacuate patients to Australia for care, concerned doing so would undermine the policy of offshore processing and settlement.

The committee also heard today from Peter Law, a former magistrate on Nauru, who described the rule of law on the island as “out the window”, and blasted the nation’s lack of free press and independent judiciary, describing it as a “rogue state”.

Dr Young is one of a group of former immigration whistleblowers who has warned new laws passed by Labor and the Coalition will prevent others speaking out, and allow further abuses to occur in detention centres.

Last month, the Australian Government passed legislation which will jail doctors and asylum seeker advocates for up to two years if they disclosures about what occurs in immigration detention. It comes into affect in July.

The Department are due to give evidence later today.

Update: This story initially said that Gillian Triggs linked the executions of Andrew Chan and Myuran Sukumaran to Australia’s poor relationship with Indonesia on asylum seeker issues. It has been changed to say she was accused of making the link.