Protesters will march non-stop around ASIO headquarters in Canberra for 32 hours to draw attention to the plight of at least 32 refugees locked in indefinite detention.
Organisers who have travelled from Melbourne are expecting a small turn-out for the march on Wednesday, with other protesters from Sydney, Brisbane and Canberra.
Sam Quinlan, spokesman for the group Walking for Freedom, said 25 to 30 protesters would march in shifts on public land to draw attention to the problem of indefinite detention and the secrecy of assessments.
"Not a massive crowd, but enough," Mr Quinlan said.
Several of the 32 refugees deemed a national security threat by ASIO have been held in immigration detention for more than five years.
But the refugees – most Tamils who fled Sri Lanka's civil war and judged to have a well founded fear of persecution – are not permitted to know the detail of the ASIO adverse assessment or appeal the finding in court.
The government refuses to issue the refugees a visa but they cannot be returned home and no other country has been willing to settle them.
Mr Quinlan said the refugees had become trapped in an "absurd bureaucracy" and the protesters would march to federal parliament later in the week in an attempt to draw further attention.
Another protester Jasmine Pilbrow said she had visited the Broadmeadows detention centre in Melbourne's north, where most of the refugees are held, for two years since moving from Alice Springs.
"Seeing the way that their hope and mental health has deteriorated has been really depressing," Ms Pilbrow said.
Fairfax Media revealed in August almost a quarter of the refugees with adverse assessments in indefinite detention – which numbered more than 50 two years ago – have threatened or attempted suicide.
The Abbott government had pledged to abandon a review set up by the Gillard government in 2012 after backbench pressure on the issue, with retired federal court justice Margaret Stone examining the ASIO findings.
But Attorney-General George Brandis announced in December Ms Stone's position would be extended for another two years.
A spokeswoman for Ms Stone said this month the review had recommended the ASIO finding was "not appropriate" in seven cases and had upheld 28 assessments.
Ms Pilbrow said there needed to be more transparency in the assessments and a quicker review process.
