A trust in South Auckland says Child, Youth and Family (CYF) is cutting young people off from its care too early, leaving them scrambling to set up an adult life.
The Dingwall Trust said young people were discharged from care at 17, a deadline that can fall in the middle of the school year, and before they can sign a tenancy agreement.
It has called for the agency to keep the young people in their care until the age of 18.
Adriana, Jackie, and Heather said they were lucky to have to be living at the Dingwall training flat, and said they did not know what they would have done without help.
"You're in CYFS because of your family - they couldn't help you, they didn't have the means to be able to bring you up ... And then leaving CYFS is like, you've had all the help there and stuff, but you're leaving it and you're going to have no help," Adriana said.
"You may turn back to your family, but your family are not ... They may not want you still, because of the past that has happened, and yeah, it's going to be hard, and you're going to go homeless, and you're going to have no-one."
Others were left with no support network to turn to.
The manager of Dingwall Trust's Care to Independence programme, Sarah Ashton, said young people were booted out of care before they could afford market rents or sign a tenancy agreement, and some of them were ending up homeless.
Ms Ashton said the Government's Youth Payment barely covered the essentials.
"These young people don't have an option, so we are pushing them into poverty as soon as they leave care - technically, they're still children, under the United Nations Convention on the Rights of the Child, up to the age of 18.
"So we're taking vulnerable children, who should have a reasonable parent in the Government, we're pushing them into poverty, and we don't want them to be too comfortable."
She said it was appalling the Government did not support the young people while they finished school.
"Once they're discharged, they could go where they get the youth payment, they could go the youth service and apply for some funding for their school fees, but they have to pay that back," she said.
"So they have to get into debt just to finish their secondary schooling, and what we think is, that's not what a reasonable parent would do."
Government neglecting its role as parent - lawyer
A senior lecturer at Auckland University's law school, Alison Cleland, said it was morally indefensible not to support the young people until they were at least 18.
"It's unconscionable, in terms of support that young people need when they've been in care - they're our most vulnerable young people, they need ongoing support: in no way should they be throwing them out of state care at 17, it's a complete dereliction of the state's duty," she said.
Ms Cleland said the Government was also in breach of the United Nations Convention on the Rights of the Child - a policy it ratified in 1993.
She said that as the corporate parent for the young people, it needed to practice what it preached.
"They're always saying, 'you take responsibility for your children and young people', and we're doing the same thing - these people are looked after by the state, so step up and take your responsibility seriously."
Ms Cleland said children in care had a number of difficulties to deal with.
She said some had been exposed to violence, abuse, and drug and alcohol addictions, which could become problems for them as they grow older.
"One of the things that's coming through very strongly in research is the number of young people who're in care who have either fetal alcohol spectrum disorder, or who have acquired brain injury ... What we're beginning to realise is how significant that is in terms of what it means when you're trying to establish yourself and be independent."
Ms Cleland said the vast majority of those who had responded to the Vulnerable Children Bill last year said the age should be raised to 18, but the Government refused.
Minister of Social Development Anne Tolley said the Government was actively considering it, and decisions were still to be made on the raising the age of state care.
Simon King, a spokesperson from the ministry, said legislative changes coming into force next year would provide some more advice and assistance to young people, which they could access until they were 20 years old.
"By law, Child, Youth and Family's custody of young people ends at age 17, but from the time the young person is 15, our social workers work on a transition plan for every young person," he said.
"Our social workers are well aware of, and have strong contacts with, the services that other agencies provide for young people once they leave our care."
Mr King said in 2012 the Government introduced Youth Service, which changed how it worked with young people getting the Youth Payment, or the Young Parent Payment, and that it was seeing encouraging results.
He said there was still more work to do, but through Youth Service, more young people were gaining the skills to help them become independent.