SARAH FERGUSON, PRESENTER: The past weeks violence on Manus Island has overshadowed the plight of another group of asylum seekers who face an equally bleak future. About 50 people officially recognised as refugees are currently detained within Australia with no prospect of being released after receiving negative security assessments from ASIO. In a scathing judgment last year, the United Nations found indefinite detention was cruel and inhuman in breach of UN conventions and ordered the detainees be released this week and paid compensation.

As Conor Duffy reports the UN's deadline has just expired and the Government shows no sign of budging.

CONOR DUFFY, REPORTER: Behind the barbed wire at detention centres across the country is a group of people with no hope of release.

They are the indefinitely detained. Among them is 32-year-old Sri Lankan Ravi entering his 5th year of detention.

RAVI, INDEFINITE DETAINEE, MELBOURNE IMMIGRATION CENTRE: So we feel we are dying here, we are going to be buried here. So our lives will end in this place.

TREVOR GRANT, TAMIL REFUGEE COUNCIL: Ravi is like everybody else, he's constantly taking sleeping tablets to blot his life out. He has often thought about suicide.

CONOR DUFFY: In the same detention centre as Ravi, another Sri Lankan man, also in indefinite detention, has written to centre management asking for a litre of petrol.

(Melbourne Immigration Transit Accommodation)

VOICEOVER READING FROM LETTER: "That I may burn my body, because I don't need my body and soul. I wish to end my life."

TREVOR GRANT: Well that man has been incarcerated, never been given a reason why he's been incarcerated for four years and his wife and little baby are still in Indonesia. His father died just recently. He has no ability to look after his family. He's slowly but surely being physically and psychologically destroyed.

PROF. BEN SAUL, UNIVERISTY OF SYDNEY LAW SCHOOL: One man drank bleach, another man tried to electrocute himself, another guy tried to hang himself with a skipping rope and another guy has cut himself and written in blood on a wall.

The only other country in the world which has anything like this, you know, the only other democracy that has anything like this is the United States at Guantanamo Bay. This is rapidly becoming our Guantanamo, a legal black hole where we send people forever.

CONOR DUFFY: Also among the indefinite detainees is a Sri Lankan woman, Ranjini. She was a child fighter with the Tamil Tigers from the age of 11. After coming to Australia, she was granted refugee status and lived in Melbourne for a year where she even got married. Then ASIO declared her a security risk. She and her two sons were put back in detention.

PROF. BEN SAUL: The UN found that those children's childhood and development as children was being severely impaired by protracted detention.

CONOR DUFFY: Ranjini's two older sons and husband are now living in the community. But she's had another child and remains inside Sydney's Villawood detention centre.

TREVOR GRANT: Baby Pari has never seen anything so far but razor wire, born inside a detention centre and has lived his entire life and it looks like he will have to spend another three or four years. The formative years of a child, as any psychologist will tell you, are the most important.

CONOR DUFFY: The treatment of self proclaimed Tamil Tigress Niromi De Soyza could not be more different. She was allowed to write a book about fighting with the Tigers and is bringing up her kids up on Sydney's leafy North Shore.

NIROMI DE SOYZA, AUTHOR 'TAMIL TIGRESS': I have come here where I have gained freedom to do, be the best I can be. Whereas in Sri Lanka I felt as if there was no hope for me.

CONOR DUFFY: While grateful for her life in Australia, she's speaking out on behalf of the indefinite detainees.

NIROMI DE SOYZA: But to this country that is not threat as many of the Tamil Tigers who have lived here, who are continuing to live here including myself have proven.

CONOR DUFFY: In many cases detainees have not been told why they are deemed a security risk. 7:30 has obtained one of the ASIO assessments, which doesn't list a specific threat but says the grounds used for indefinite detention are being a member of the Tamil Tigers and being involved in LTTE [Liberation Tigers of Tamil Eelam] activities including propaganda and recruitment activities and being ideologically supportive of the LTTE and its use of violence to achieve political objectives.

Advocates for the detainees question these assessments.

TREVOR GRANT: Well, there's many LTTE fighters who are living in the Australian community, hundreds of them, in fact. So they're not regarded as any problem.

CONOR DUFFY: What if one of these refugees was released and committed a terror attack?

PROF. BEN SAUL: Well, you can say the same about any Australian citizen or permanent resident who might be dangerous. You know, we don't lock up without charge or trial or effective judicial protection any Australian who the police might think is a danger to national security.

And that's another five refugees who have been in detention for...

CONOR DUFFY: Barrister and Professor of Law Ben Saul took the case of the indefinite detainees to the UN, which found in their favour, describing Australia's treatment of them as cruel, inhumane and degrading.

PROF. BEN SAUL: By this week Australia is required to release the refugees into the community on security conditions if that's necessary in individual cases. But also to compensate them for almost five years of illegal detention and to rehabilitate them because they're suffering from such severe mental stress.

CONOR DUFFY: Professor Saul says the case was won on the lack of judicial oversight and the fact refugees aren't allowed to see detailed evidence against them.

PROF. BEN SAUL: These are more than 150 violations of some of the most important human rights known to international law; freedom from arbitrary detention, the right to habeas corpus and adequate judicial protection by the courts and freedom from cruel, inhuman or degrading treatment or punishment.

CONOR DUFFY: ASIO and the Immigration Minister declined to respond to questions, but in a statement the Attorney General George Brandis said the Government was working on a response to the United Nations.

(Excerpt from statement)

VOICEOVER: "The Australian Government is considering its response to the UN Human Rights Committee's views...ASIO's role is to access whether it would be consistent with Australia's security for a person to be granted a visa. ASIO's priority and responsibility is to ensure that Australia's security is not compromised."

CONOR DUFFY: Advocates believe the UN ultimatum is likely to be ignored. Both major parties recently united to pass laws enshrining indefinite detention and overturning a successful appeal to the High Court.

NIROMI DE SOYZA: Sometimes I look and think why do I deserve to be outside and have the best life I can and where these people should be held back behind bars and not be able to live with hope that one day they can lead a normal life.

SARAH FERGUSON: Conor Duffy reporting.

Read the Attorney-General's response to 7.30 on this story.