The Prisons and Probation Ombudsman (PPO) annual report has revealed that during 2017/18 it investigated two deaths of young people accommodated in secure children's homes (SCH).
This is the first time it has investigated the deaths of children in SCHs.
One of the teenagers, referred to as Child R, hanged herself in her room at a SCH in County Durham, in February 2017, where she had been placed by Durham County Council.
The girl was at serious risk of suicide and self-harm and during her seven month spell at the SCH she had tried to take her own life or self-harm on more than 100 occassions.
The PPO report states that while staff were "caring and committed" there were "deficiencies" in the way her case was managed, including a lack of risk assessment.
Checks on her safety were also not robust enough, states the PPO report.
"Child R was the first child to take her life in a SCH in over 20 years. We found the staff at the SCH were caring and committed, but there were deficiencies in the way Child R was managed," states the report.
"The suicide and self-harm measures lacked a detailed risk assessment and were not sufficiently responsive to changes in Child R's risk, and there was no coherent framework for her mental health care. The wellbeing checks were inadequate: most lasted only a few seconds and were not sufficient to establish that Child R was alive."
Margaret Whellans, Durham County Council's corporate director for children and young people's services, said: "Our thoughts remain with the family of the teenager involved.
"We are co-operating fully with the coroner's inquest into her death and it would be inappropriate to comment while this is ongoing."
The ombudsman also investigated the death of a boy, known as Child S, at a different SCH in February 2017. He was found dead in his room with suspected sudden arrhythmic death syndrome (SADS), which is when someone dies from cardiac arrest and no obvious cause can be found.
Despite suffering a seizure the previous month checks on his welfare, through the observation panel on his door, were not carried out frequently enough.
"We found that the wellbeing checks carried out on Child S were ineffective as they failed to identify that he was no longer alive," states the report.
"Troublingly, some staff recorded that checks had been carried out when they had not. Staff also seemed unclear about the purpose of the checks and how they should be carried out."
According to the Secure Children's Homes website there are 15 SCHs throughout England and Wales accommodating males and females aged between 10 and 18.
A young person can be referred to a SCH because a local authority has serious concerns about their welfare or behaviour.
