Parents whose children are in state care have to pay hundreds of dollars to spend time with them.

A mother whose son who was placed in state care because she was in a violent relationship is forced to pay $92 dollars an hour to visit him.

The woman - who has previous criminal convictions - says she has learnt from her mistakes and says she is a really "good mum".

"I am not a perfect person but I am a good parent. And I have never ever hurt my child."

The woman, who we can't identify for legal reasons, has also revealed to the Herald on Sunday she is one of many parents who can't afford to pay the fee to see her son.

"The process is I am advised as to when I can see him at a supervised centre through Barnardos. I pay an hourly fee of $92 dollars. There is an initial assessment process you have to go through which costs $250.

"It's had a huge financial burden on me."

A leaked Barnardos obtained by the Herald on Sunday outlined the cost of each service: Assessment: $250, Session: $92/hour, and Changeover: $60 pickup and drop off.

All services had to be pre-paid before the visit.

The woman, who is on a sickness benefit and a tight budget, says she is left with $27 at the end of each week after she's paid rent and bills.

Ruth Herbert, a co-founder of The Backbone Collective, and a voice for women of domestic and sexual violence, says it's "offensive" that families are required to pay.

"I don't have a problem making abusers pay. There is no evidence the mother has harmed her child so this is wrong," she said.

"You are already punishing them by taking away their child and preventing them having a relationship and if they can't afford to pay - that is fundamentally wrong."

The woman said it is heart-wrenching not knowing where her son is and who is caring for him.

She said the hourly visits at Barnardos are sporadic and impersonal; the last being six months ago.

"I could be with my son having a laugh and chuckle – and there is someone sitting right beside us. A stranger. It's a really unfriendly environment, it's not natural," she said.

Herbert said visits were staggered so the child's "drop off" doesn't coincide with the parents' arrival.

Another woman told the Herald on Sunday she has paid $1200 this year to see her daughter. The girl lives with her father in another city.

"The court system is ridiculous- it's only if you have deep pockets you can fight them. The supervised fee is $80 each time. It's a five-hour drive because I live in another city for work. We meet in public places but it gets expensive".

A Barnardos spokesperson said the majority of referrals for supervised contact were from the Family Court.

"The Family Court funds the assessment for supervised contact, and a set number of supervised contact sessions.

"Supervised contact is staff-intensive, as the reasons for supervision are related to child safety concerns."

The assessment fee is for risk assessment by Barnardos that determines suitability for the service. Both adult parties are required to agree to the safety of the rules in the centre, and this includes around photographs, food, treats and gifts.

A spokeswoman from Oranga Tamariki said fees for services can be paid on a client-by-client basis.

"When the court orders that contact be supervised by an approved organisation, the cost of the sessions is paid for by the Government, unless ordered otherwise by the courts."

At 31 March 2018, there were 6250 children and young people in the care and protection custody of the Oranga Tamariki Chief Executive.

The woman, who has a protection order against the father of her child, is happy for him to have supervised contact with their son.

"Every parent has the right to see their child," she said.

The mother added: "I will move mountains for my son but it's got to stop at some point."