Amnesty International says Australia must scrap remote immigration detention centres and take other measures, in order to meet human rights standards.
In a highly critical report following an 11-day tour of some of Australia's detention facilities this month, Amnesty said it was undeniable that human rights violations were occurring.
"Amnesty International remains appalled that this policy has continued for so long," the human rights group said.
Asylum seekers should be detained only for a maximum of 30 days once they reach Australia and remote centres should be closed as soon as possible, Amnesty said.
The report called for a shift towards processing asylum seekers in the community to be expedited with long-term detainees, families and unaccompanied minors moved out as a priority.
The ability for asylum seekers to communicate with the outside world also needed to be significantly improved, it said.
Amnesty painted a picture of Australia's detention centres as places where suicides were commonplace and sleeping pills and other medicines were widely used so detainees could get through each day.
It was "overwhelmingly evident" that the uncertainty over how long detention would last, along with fear and monotony was more than most people could cope with, Amnesty said.
It said the Curtin centre in Western Australia should be closed immediately for immigration detention due to its remote and isolated location as well as the extremely hot and dusty conditions.
More than half the phones at the centre tested were not working and the internet was so slow that downloading a file sent by a lawyer is often impossible, it said.
The Northern Immigration Detention Centre in Darwin, where a number of detainees last year sewed their lips together and went on hunger strike, was "totally inappropriate" for detention of asylum seekers, Amnesty said.
Even the state-of-the-art Wickham Point centre near Darwin that opened in December came under fire from the human rights group, which said the level of security inside and outside was completely unnecessary.
In an emailed response to questions, a spokesman for Immigration Minister Chris Bowen said the government wanted to see fewer people in detention and believed they should remain in the centres for as little time as possible.
"In the past 16 months we have moved more than 3600 children, families and vulnerable people into community arrangements, either into community detention or on bridging visas with work rights," he said.
"People who remain in detention facilities are treated humanely and have appropriate access to health care and education, as well as a variety of activities and excursions," the spokesman said.news.ninemsn.com.au
