Most Australians support the camp policy

The policy has been in place since 1958, but in recent years has been the subject of growing international criticism as the numbers involved escalated.

More than 3,500 people are now in detention, including many women and children.

While some have their applications processed in just a few weeks, others have been held for months.

The three largest detention centres are in the remote desert areas of Western and South Australia. Others are in Sydney, Perth and Melbourne. Plans are under way to establish more camps as the number of illegal immigrants rises.

The detention centres are run by a private security firm contracted by the Australian Government. The regime has been criticised by human rights groups, as well as former employees who have worked in the camps.

The government, stung by the negative publicity, hit back with its own media blitz

There have been allegations that refugees have been abused, both physically and verbally. Those who have spent time in the centres say that anyone who complains is labelled a trouble-maker.

Sporadic hunger strikes have been common, with some refugees sewing their lips together in protest at conditions. Others have attempted suicide.

But the truth about what goes on inside the centres is extremely hard to verify, as the media are effectively banned from talking to the refugees.

There have been plenty of escapes too. Refugees have tunnelled and dug their way out of several camps, and a mass breakout at the Woomera detention centre in South Australia saw hundreds of asylum seekers stage a peaceful but noisy occupation of the local town centre.

At times the protests have been more dramatic, as tensions within the camps boil over into violence. The authorities have responded to riots with water cannon and tear gas, images that have been broadcast around the world.

'Un-Australian'

But the government, stung by the negative publicity, hit back with its own media blitz, displaying weapons allegedly manufactured by some refugees for use against security staff.

In June, members of a parliamentary committee examining human rights standards in the centres said they were shocked by what they found. If the huge gates and high fences topped with razor wire were not bad enough, the conditions inside the camps sparked strong criticism.

"Un-Australian" is how opposition Labor MP Colin Hollis described the situation.

"No-one can visit these centres without being profoundly affected - nothing prepares you for the visible impact of visiting such centres," he said.

About 80% of those who have their applications processed are allowed to stay in Australia, at least in the medium term. But it is an expensive business. Last year the system to manage asylum seekers cost the Australian taxpayer about A$100m (US$53m).