A mental health nurse has broken her silence about working inside Australia's immigration detention system.

Ena Grigg, who has been nursing for almost 40 years, has told Lateline she saw despair and self-harm every day while caring for detainees at the Northern Immigration Detention Centre in Darwin.

She says if she showed concern for her patients she was told to "harden up".

Ms Grigg's personal account of a system under strain comes as more people people are being released into the community detention, and a large new detention centre prepares to open.

This year, motivated by desire to see more of Australia, she signed up to a three-month contract to work at the immigration detention centre in Darwin as a mental health nurse.

"I was not very supportive of people coming to live here that way," she said.

"I used to say I was one of the first people to say why don't we send the boats back to where they come from that will stop them, but it was my ignorance.

"I am really ashamed I thought that way."

Two weeks after she was presented with depression and self-harm every day, Ms Grigg's world view turned around.

She now believes mandatory detention is wrong.

"Being locked in a prison with not knowing how you are going to get out or when you are going to get out or why you are even there, and not getting any answers as to how they can get out is driving people mad," Ms Grigg said.

She says detention is sapping people's will to live. She was dealing with severely depressed people every day - a situation she is still finding traumatising.

"For me I found it very depressing, very despairing. Just the level of despair that seems to ooze out through the floor and through the building," she said.

"I have seen people write rude things on the wall in their our blood. I have seen people cut their hair, write f*** you in their hair and that on the wall," she said.

"Just cutting themselves."

Speaking out

It is rare for a frontline worker inside the immigration detention system to speak out.

Staff sign confidentiality agreements but Ms Grigg says she wants Australians to know her story, and her concern for the mental health care of asylum seekers.

"Literally I was told to harden up, but I can't do that when I see despair," she said.

"I am driven to do something to stop it and I just can't rest, I can't go home at the end of the day when people are threatening to hang themselves.

"I have to stay and talk to that person. I can't stand that sort of stuff."

Australian College of Mental Health Nurses chief executive Kym Ryan says people rarely speak out because they are scared about their experiences.

"I think Ena is very brave speaking out in relation to her experiences in particular in the Darwin detention centre," he said.

The Australian College of Mental Health says the level of mental health care inside immigration detention centres is not good enough.

Ms Ryan says Ms Grigg's story is not an isolated one.

"From what I understand, in relation to the services being provided currently in the detention centres, they are less than any standard across any other service in the country," she said.

"And I think people are feeling very compromised in relation to their own practice standards and their own ethical standards."

Low on resources

The private company contracted to provide healthcare in detention centres has admitted it has been stretched for resources.

International Health and Medical Services (IHMS) wrote to the Immigration Department in October, proposing better access to a pool of psychiatrists.

"The increasing surge in clients, particularly in remote locations, has placed stress on the limited network of providers," it wrote.

A new mental health policy was introduced in November 2010 called the Psychological Support Program (PSP).

The program is suppose to identify and support immigration detainees who are at risk of self-harm and suicide, but there are concerns it has not been properly implemented.

The director of the Monash University Centre for Developmental Psychiatry and Psychology, Professor Louise Newman, says due to the high staff turnover there has been some issues in ensuring all staff are aware of the policy.

"We have got very fragmented detention system. We have very remote locations we have rapidly changing staff.

"So there have clearly been some issues in making sure that all staff...work within it have had the training and support that they need."

The Immigration Department says mental health policies continue to be reviewed with experts, and mental health training has recently been revised and delivered to staff across the detention network.

It says it and IMHS ensure people in detention have access to mental health nurses, psychiatrists and psychologists.

In a statement, the Department says the centres were operating "at a standard equivalent to that available in the general Australian community".

System under strain

Large boat arrivals over the past year have taken the immigration detention population to almost 5,000.

The Federal Government has moved to ease pressures by announcing bridging visas for asylum seekers who arrive by boat.

At least 100 people will be released into the community every month.

"At the moment we are waiting to see the potential impacts of these changes as they become known on the number of arrivals," Professor Newman said.

"It is likely that they will be continuing at least for the same level if not more arrivals - that is somewhat unclear."

Mental health nurses say they are concerned about damaged people being released into the community.

"Approximately 90 per cent of these people at some point will be given a visa to remain in Australia," Ms Ryan said.

"And whilst we are not providing the mental health care they require now within the detention centre, it will be the responsibility of the community to pick up that cost and that bill in human costs when they go out to live in the community."

Ms Griggs fears the anger and mental health distress of asylum seekers are setting them up to fail when they enter the community.

"They are no different from anyone else. They are frustrated. They are hurting. They need support and sustenance like the rest of us," she said.

"I think that has been the biggest thing for me to realise is they are no different than anyone else just because we are Australian.

"We are no better and when I see what we do to these people I think we are as bad as what their countries are."

A new immigration detention centre will soon open near Darwin to care for 1,500 single men.

The Immigration Department hopes new activities at the centre will reduce the stress of indefinite detention.