In an exclusive interview with Dateline, one former staffer said she was hired to work on both Nauru and Manus Island without undergoing any application process or training.
The university student, identified as Marie, said she was shocked by the overcrowded and unclean conditions when she arrived on Nauru.
“They put us into the camp and said ‘just go and mingle’,” she said.
“I didn’t know what to say to them or how to speak to them.”
Another former employee alleged that Salvation Army staffers had fabricated management plans for detainees.
The Salvation Army denied the claims, but declined from commenting further.
It comes a week after a migration agent who worked on Manus Island told Dateline she was told to lie to inmates.
Liz Thompson, a former migration agent turned whistleblower, described the administration of the Manus Island detention centre as 'ridiculous' and claims she was instructed to tell detainees their only option was resettlement in Papua New Guinea.
“They (detainees) watch the news, they read the newspapers, they watch what’s going around in the camp, they know there’s no decision from the Papua New Guinean Government on resettlement," she told Dateline's Mark Davis.
"So what that means is… you’re never getting out of this camp, it’s indefinite detention."
A spokeswoman for the Minister for Immigration and Border Protection, Scott Morrison, denied that Manus Island detainees had been told they would not be resettled in PNG.
“With regard to reports that the transferees were advised that they will not be settled in PNG, the Minister has been advised that those reports are false," she said in a statement.
The allegations come as the Immigration Department faced questions on the recent riots on Manus Island from a Senate Committee.
The department head described detainees pushing down fences and throwing rocks before police discharged a gas canister and fired warning shots.
Immigration and border protection secretary Martin Bowles said work was needed to uncover what happened.
"There are a range of other reports, there are interviews that need to happen with the independent reviewer to start to work through the myriad of information that's out there," he said.