A mother whose daughter was put in a secure children's unit for her own safety has likened it to a "child's prison".
The "vulnerable" teenager from Wales was placed 250 miles away from home and is held with youth offenders.
The Children's Commissioner for Wales said new specialist residential care placements for children with complex issues were needed urgently.
The Welsh Government said an urgent increase in places was being looked at.
The girl's mother, who cannot be named to protect her daughter's identity, said the council's decision to place her in the home under a secure welfare order was "terrifying".
At the time, the teenager had been drinking and self-harming and the local council said she was at high risk of sexual exploitation.
"There were no beds available in the UK during initial court proceedings; a placement was actually found while we were in court," she said.
"She was an absolute mess, it was absolutely awful. She didn't cope at all.
"We don't have enough contact. She wants more contact but it's difficult for me to go there as often as we'd like as I have other children at home."
The mother said the environment of a secure children's home was not appropriate.
"It's a child's prison isn't it? You have contraband, you have methods of control, you have all this terminology and it's scary.
"They lock them in their rooms at night for 12 hours."
The mother said it was "really worrying" her daughter was in the same place as those who had committed crimes.
"She's a very vulnerable girl and could be easily influenced by these children and they could have committed crimes from murder to assault - you just don't know - and it can't be disclosed to me, so I don't know who she's mixing with and how that's influencing her. I don't believe it's right that they're mixed together."
She said she was concerned about the teenager's long-term mental health.
"Our lives are on hold really, it's like a never-ending nightmare."
Away from home
There is one secure children's home in Wales, in Neath, and 14 in England.
In the last year, 20 secure welfare placements were made for children from Wales involving 18 children. Ten of those placements were in secure homes in England.
The homes are run by local authorities for children over the age of 10 who have either:
- been convicted of serious crimes or
- been placed there by the family court for their own safety or the safety of others following an application from a local council.
The Children's Commissioner for Wales said the current provision for secure homes was inadequate and new therapeutic residential services were urgently needed in the country.
Prof Sally Holland told BBC Wales: "We need to stop looking at it as either a mental health setting or social care setting and think about how, together, those specialist services can provide the right care for those children [with a high level of emotional and mental health needs]."
She said the needs of this small number of vulnerable children were not being met and that she had raised it with government "frequently".
A Welsh Government spokesman said: "We are working with partners to develop new approaches to therapeutic care for children with particularly complex needs and challenging behaviours.
"These include specialist residential placements for children who are at risk of going into secure accommodation, and step-down provision for those moving on from a secure placement."
He said the Children's Residential Care Task and Finish Group, on which the children's commissioner is represented, was urgently considering how best to increase capacity in these areas.