More than half of alleged foreign sex slavery victims in Australia are left without government support due to legislation that gives the Australian Federal Police (AFP) the authority to exclude suspected victims from the aid program.

In order to be entitled to the Department of Social Services (DSS)-funded Red Cross program that offers medical and psychological aid, accommodation, living allowance and English language classes, the victim has to be both willing and able to make a contribution to the prosecution process.

Yesterday the ABC reported claims that the requirement puts victims' lives at risk due to the danger of reprisals from "ruthless" people-trafficking syndicates.

But anti-human trafficking organisations are concerned that alleged victims who are willing to endanger their lives are often pushed off the Government's Support for Trafficked People Program because the police may not assess them as an "appropriate witness".

Kathleen Maltzahn, founding director of Project Respect, which supports trafficking victims, said she had worked with women who had undoubtedly been trafficked but did not qualify as an "appropriate witness" in the eyes of law.

"If the woman doesn't know the proper names of who trafficked her, if she doesn't know the address of the brothel, can't remember dates, if she's confused about what happened [and] when — partly because of trauma — that might mean that with the best will in the world she might not be a credible witness in court," she said.

"You can talk to women who don't even know what suburb they've been held in and, indeed, I've spoken to women who haven't always been sure what states they've been in. So they often can't be witnesses."

Ms Maltzahn said these women were then left to fend for themselves in the same country where they had been subjected to severe sexual violence.

"Women who have experienced tremendously serious violence in this country can spend years in limbo which really doesn't aid their recovery," she said.

"It's hard to believe that we can't afford as a country to really allow women to recover from this very serious violence ... given that violence was perpetrated in this country."

46 out 88 women left support program in last financial year

The Coalition Against Trafficking in Women in Australia says the laws put unrealistic expectations on the alleged victims.

"The assumption that they can just lay out for you the whole organised crime on a platter to explain how they were trafficked — we know that that's unlikely, extremely unlikely," the Coalition's Meagan Tyler said.

Over half of the alleged victims referred to the police are falling through the cracks, statistics provided to the ABC by the DSS and Department of Immigration and Border Protection (DIBP) show.

In the 2014-2015 financial year, out of 88 people on the Support Program, 46 left.

The same year, of the 38 new clients who entered the program, 20 were exited, the DSS spokesperson said.

The DIBP spokesperson said eight permanent Referred Stay visas were granted to victims who were seen as being in danger when they return to their country of origin.

However, only half of those visas went to the victims and the other half to their dependents.

Nine victims were granted Criminal Justice Stay visas and 15 Bridging F visas to cover the police assessment period were given.

Law asks victims to 'prove themselves'

Lena Sivasailam-Pichler from Project Respect visits about 90 legal brothels in the Melbourne area.

Her work involves knocking on brothel doors, counting on being allowed entry so she can win women's trust and assist them in escaping slavery.

She said even when the organisation did succeed in referring the victims to the police, it was not always clear why they were exited from the program.

"Last year we had eight women who were on a Support Program — all of them were exited from it. And we really don't know why they were exited from it," she said.

Ms Tyler said a system that was "forcing victims into cooperating" was suspicious of any potential victim.

"I think there are concerns in the current climate, certainly, that victims of trafficking need to prove themselves somehow," she said.

"I think that seems to be where it comes from in terms of the national narrative of immigration — as horrendous as it is in this country — [it] seems to distrust people who have come from anywhere else."

Though the Support Program is only funded to provide support for victims who fit the eligibility criteria for the government aid, a spokesperson for the Attorney-General's Department said there were "other appropriate support frameworks and legal and migration options, if required".

Australian Catholic Religious Against Trafficking in Humans (ACRATH) executive director Christine Carolan, who works with human trafficking victims, said while this was the case, the 20-day transition period granted to find alternative means of support was "very difficult".

"That's a very tricky point of movement for somebody to go from the Red Cross program where they're given good support, quality support, into a space where they have to fend for themselves," she said.

The AFP and Australian Crime Commission declined the request to answer any specific questions, saying they would refer the ABC to the Attorney-General's Department.

How the support system works

The Assessment and Intensive Support Stream sees that all trafficked people referred by the AFP to the Support for Trafficked People Program are eligible to receive 45-day support, regardless of whether they are willing or able to assist with the investigation. If the person does not have a valid visa, they are granted Bridging F visa to cover that period.

The Extended Intensive Support Stream provides access to a further 45-day support for trafficked people who are willing but not able to assist with the investigation.

The Justice Support Stream provides support for trafficked people until the investigation and prosecution process is finalised. Their stay in Australia throughout that period is covered with Criminal Justice Stay visa.

The Temporary Trial Support Stream provides support for trafficked people giving evidence pertaining to a human trafficking or slavery-related prosecution. A person who has made a contribution to an investigation or prosecution process may be eligible for a Referred Stay (permanent) visa.