A former mental health worker at Australia’s detention centre on the island nation of Nauru has condemned Canberra’s policies towards asylum seekers following allegations of sexual abuse and an outbreak of self-harm and attempted suicide at the facility since inmates there were told they would be resettled in Cambodia.

“There are lots of people who work in Nauru for the money, working with children, and [background] checks aren’t done,” the aid worker, who requested anonymity, said. “It’s terrible. It changes your life, [being] over there.

“The bullying is shocking by the security staff.… The conditions of the camp are unbelievable,” she said, going on to describe numerous instances of asylum seekers being deliberately denied medical care by Australia’s immigration department.

“There was a man flown to Darwin for treatment who was flown back [to Nauru] against medical advice. He was found in his tent covered in blood and excrement.… At the end of the day, it’s all because of immigration,” she said.

The comments follow a rash of attempted suicides and self-harm in the facility. This week Fairfax Media reported allegations of sexual abuse of women and children on Nauru, including a threat of rape and children being forced to perform sex acts in front of a guard.

An adult Iranian couple on Tuesday evening swallowed washing powder and pesticides, bringing the number of attempted suicides since Friday to at least four, while there have been at least 12 cases of self-harm. The two Iranians have not been heard from since being transferred to the medical centre.

According to a refugee on the island, the couple’s 4-year-old daughter is in a clinic and believed to be in a serious condition, with no appropriate medical treatment available on the island.

“This is all about pushing them to the brink, pushing them to the absolute edge. The arrogant Australian government wants them to go back [to their home countries]. I don’t get it; [the government] must be psychopaths,” the aid worker said.

“The immigration policy is that refugees and asylum seekers on Nauru are not entitled to any medical care above and beyond what locals on Nauru are allowed. But they send very, very sick people there.”

A female Iranian refugee living outside the detention centre – one of 250 people granted temporary residency on the island in recent weeks – yesterday said that it was common for security guards employed by Australian private security firm Wilson Security to commit sexual assault and threaten protesters.

“When I was in there, they just flirted, but now [it has gotten worse],” she said. “The security used bad behaviour I will never forget.”

“The asylum seekers had a peaceful protest.… But [Wilson Security] were trying to start a fight … the Nauruan [security guards] were coming to them with something sharp while women and children were at the front,” she said.

A worker at the Nauru detention centre told Fairfax on Tuesday that she often saw children sitting on guards’ laps.

“I was told by an Australian guard who was friends with the locals that there was an imminent danger when the asylum seekers were released in regards to violence and sexual abuse,” she said.

GT Media, a PR firm contracted by Wilson Security, yesterday referred questions to Transfield Services, a huge Australian company with close ties to the government and which holds a number of military procurement contracts.

A spokesman for Transfield referred questions to the office of Australian Immigration and Border Protection Minister Scott Morrison, who signed the agreement to send the refugees to Cambodia over flutes of champagne on Friday in Phnom Penh.

A spokesman for Morrison did not respond to repeated requests for comment. However, Morrison yesterday told Fairfax that there was “little or no substantiation” to the allegations, adding that his department would conduct an investigation and that he would be “pretty damn cross” if evidence of abuse was uncovered.

In submissions to the ongoing Australian Human Rights Commission inquiry into “offshore detention”, children in the camps also accuse staff hired by charitable organisations, such as Save the Children, of abuses.

A child protection worker writes in one submission: “Save the Children hires local Nauruan people who have very close contact with children.… Children have been sexually assaulted and threatened with sexual assault, and they are not allowed to leave the camp, even with family members able to care for them here.”

The former aid worker corroborated several of the allegations of abuse.

Sarah Hanson-Young, immigration spokeswoman for the Australian Greens, yesterday called for the Nauru detention centre to be closed after a motion passed in the Senate calling for the release of files related to abuses on the island.

“The Australian government is actively and intentionally destroying women and children on Nauru,” she said. “Despite the minister’s claims when it comes to sending people to Cambodia, it’s clear these people have no real option.”

“The Abbott government has them over a barrel, and the choice between one hell or another is clearly no choice at all.”

According to Australian media, Nauru’s minister for finance, David Adeang, told the New South Wales Supreme Court in Sydney that the country would be unable to operate by the end of the week as the politically connected Australian bank Westpac had frozen the government’s accounts.

New Zealand’s Foreign Ministry confirmed to a radio station there yesterday that it had frozen aid to Nauru, which owes more than $26 million to the US-based Firebird Global Master Fund, which bought the country’s debt from Japan.

In the middle of this political wrangling, the refugees have simple requests.

A Syrian child in Nauru, speaking through a translator, said that he would like to go back to school.

“I left my country because it has wars and is bad now. I want to go to school and be a doctor, but here there is no [good] school and I blame Australia.”