The Australian government is maintaining a “charade” on Manus Island by pretending to process the claims of asylum seekers when in fact the detention camp is designed to be nothing more than a deterrent to others, a former staff member has told SBS Dateline in an interview to be aired tonight.

Migration agent Liz Thompson, who was working on the island during last week’s violent attack on detainees by G4S staff, locals and PNG police, tells Dateline that she was part of a team of agents employed by the Australian government to prepare refugee applications for detainees at the centre.

She says the process she was involved in was a “farce”.

“It’s not designed as a processing facility, it’s designed as an experiment in the active creation of horror, to deter people from trying in the first place,” she tells Dateline’s Mark Davis.

Tension came to head on Manus Island last week after detention centre staff were instructed to lie to asylum seekers to maintain an illusion that their claims were being processed and they would be settled in PNG, Thompson says.

“The script is a farce. We are told to… not talk about third country options, to keep them focused on resettlement in PNG – that resettlement in PNG is what’s going to happen.

“We all knew that this was ridiculous, but we were lying to people, and we were told to keep that message going, to keep it clear.

“But [the detainees]know that’s not the case. They know there is no decision from the PNG government on resettlement. So what that means is: you’re never getting out of this camp. This is indefinite detention. While we play this charade.”

Thompson says she was supposed to be assisting asylum seekers to prepare their claims for presentation to the PNG government, but all interview arrangements, travel and briefings were organised by Australian Immigration department staff, who she says also delivered a script to migration agents and lawyers for presentation to group meetings of asylum seekers.

She says she returned home late last week after resigning from her position in disgust at Australia’s handling of last Monday’s attack, which left Iranian asylum seeker Reza Berati dead, another man in a serious condition with a slit throat, and dozens of others injured.

“The process … cannot continue after an asylum seeker has been brutally murdered in the care of the people who were supposed to be looking after him,” she says.

Thompson has worked with asylum seekers in the past and is a refugee advocate, and says she nominated to work at the island because she thought she would be able to help the detainees.

“There are well-meaning people, including lawyers and migration agents, who think ‘the guys need us we can’t leave them now’. They believe they should be there, because they believe there’s a process.”

But she says she realised after last week’s violence that “we cannot assist them by lying to them about what’s happening and by feeding them Immigration’s fantasies, things that they know are not true”.

“These guys are smart, they know what’s going on, they know they’re being lied to, and having that stuff come to them from Immigration, from us, is just part of the active creation of horror.”

“That’s what Manus Island is: it’s the active creation of horror in order to secure deterrence. And that’s why Reza Berati’s death is not some kind of crisis for the [immigration]department – it’s actually an opportunity, an opportunity to extend that [deterrence]logic one step further, to say, ‘this happens’.”

“It was clear to us that we were being used as part of that logic… and we didn’t want to be part of it anymore,” she says.

Thompson believes that her team was sent to Manus Island so that the Australian government could say that processing had begun at the centre, but that the fake processing had in fact exacerbated tension at the camp.

“[The government wanted to be able to say] the interviews have begun, everything’s happening. But what’s not happening is any kind of clarification about where [the asylum seekers]are going to end up.

“We couldn’t give [detainees]any information that was useful other than: well, here’s your refugee status determination – we’ll give it to somebody, we don’t know where it will end up. It’s done, but we don’t know where you’re being settled.

“The process doesn’t lead anywhere except to indefinite detention.”

Watch the full interview on Dateline at 9.30pm tonight on SBS.