Jersey's Government has been accused of breaking the law after it placed a teenager under the age of 16 in the islands adult prison.
The child is being held inside La Moye - a move described by the Children's Commissioner as a "breach of human rights" and against the law. Deborah Macmillan has written to the government saying the decision to detain the teenager in Jersey's jail is not appropriate.
ITV News understands the teenager had formerly been held at the young offenders institute at Greenfields, but was moved to the adult prison in recent months.
The Children's Commissioner has visited the wing at La Moye where it was proposed the child would stay.
She said: "It is also worth noting that the 2012 HMPI inspection of La Moye was damning in terms of holding juveniles in that facility, which is why the Young Offenders Institute closed in the first place, and Greenfields was built in its stead.
"The current situation, therefore, would indicate that we, as an Island, are in fact going backwards in this regard, and directly against inspectors’ advice."
She says it breaches the United Nations Convention on the Rights of the Child which states:
“Every child deprived of liberty shall be separated from adults. A child deprived of his/her liberty shall not be placed in an adult prison or other facility for adults".
The Children's Commissioner was given the minutes from the meeting where it was decided to place the teenager in La Moye, which she said "lacked any substance or detail" and did not show the Panel had taken into account the best interests of the teenager.
She added: "In the absence of a dedicated youth facility at HMP La Moye, it seemed to be felt that the only available options were to hold the child in segregation at La Moye or within the current adult population. Both of these options would present serious risk of harm to the child, in terms of mental health, and would be a breach of their rights.
"Therefore, my strong advice to both Ministers was that moving the child to HMP La Moye would be a breach of their human rights and a violation of obligations arising in respect of Jersey from the UNCRC. It was also my assessment that this would be incompatible with Article 27 of the Prison (Jersey) Law 1957."
In a statement, Jersey's Home Affairs Minister Deputy Gregory Guida said: “We are unable to comment on individual cases and must ensure that the privacy and identification of any young person, under the age of 18, is respected at all times.
"We aim to secure people on custodial pathways in the institutions that provide the best protection to themselves, staff, and the public."
ITV News approached Jersey's Children's Minister, Deputy Scott Wickenden but he declined to comment.