The children’s commissioner has been called on to intervene in the case of a vulnerable teenager alleged to have been the victim of a catalogue of failures at the hands of social workers, medical authorities and police.

Laura*, 16, who nearly four years ago is thought to have been the youngest child ever to be placed in a secure hospital in England, has allegedly been sexually abused since she was 12 – always while supposedly under the protection of children’s social care in Sheffield. She is now confined to the seclusion unit of a psychiatric hospital under suicide watch.

Her mother Susan*, who has spoken to the Observer, says she fears every day that someone will knock on her door and say Laura has been found dead. Laura was taken into care because Susan was struggling with her daughter’s behaviour. Susan, herself a victim of child sexual exploitation, desperately wanted her child to be protected from the same fate.

Campaigners say they have contacted Anne Longfield, the children’s commissioner for England, as a “last resort” after battling to help the teenager and her family for the past three years. Kathryn Kelwick, an outreach worker who dealt with victims of the Rotherham child abuse scandal, claims Laura was “horrendously exploited” during two periods of residency at a children’s home in Sheffield. Evidence gathered by Kelwick and Laura’s family suggests that while living at the children’s home Laura was able to come and go as she pleased, despite often showing signs of having been abused when she returned. Those exploiting the teenager were allegedly able to call for her in taxis sent to the home.

In the first of these periods, Kelwick claims, “it took months for authorities to sit up and take notice”, and by the time they did, the then 14-year-old “had been sexually exploited by over 40 adults”. According to the family, social services “turned a blind eye” to the abuse, and they claim that South Yorkshire police failed to take any meaningful action to pursue those exploiting the girl.

The level of care and supervision she has received at [the hospital] has been appalling and she has been [treated] worse than an animal. Kathryn Kelwick, campaigner

The teenager’s MP, Louise Haigh, who has been regularly updated on Laura’s plight, has said that she regards the case as “deeply disturbing” and says she has raised it on numerous occasions with senior officials at Sheffield social services. Alan Billings, the police and crime commissioner for South Yorkshire, has described Laura’s plight as “a shocking and sad story”.

Despite this, Sheffield Children Safeguarding Partnership has turned down a request for a serious case review into Laura’s treatment, arguing that it would not be “appropriate”.

Laura’s trauma was so severe, says Kelwick, that she had to be taken out of the children’s home and placed in secure accommodation for a year. At the end of that year she was sent back to the same children’s home and “within days of being there” the cycle of sexual exploitation had started for a second time. At one point Susan gave the police the names of 21 suspects – but, she claims, police did little to investigate. Only one of the suspects was questioned, belatedly, and officers are said to have accepted his word when he said he thought Laura was 18. At the time she was 14.

Eventually South Yorkshire police made Laura the subject of a police protection order and she was again placed in secure accommodation. But by this time the teenager’s mental health was so poor that she had to be sectioned and then detained at a private psychiatric hospital.

Kelwick claims in her submission to the children’s commissioner: “The level of care and supervision she has received at [the hospital] has been appalling and she has been [treated] worse than an animal. She attempted suicide by taking an overdose twice in four days and still she wasn’t monitored. Currently she is being kept in segregation to keep her safe. She has been held in a room for five weeks with only a mat to sleep on and a toilet. She is being guarded by three to four males from agencies that do not interact with her.”

Kelwick, who manages post-abuse services at the Swinton Lock charity in Rotherham, said: “The way Laura has been treated is an absolute scandal that has to be addressed.

“She has been dreadfully let down from the moment she went into care. Four years on, she is an incredibly damaged child without a shred of hope for the future.”

Kelwick highlights the irony that Laura’s mother wanted to protect her daughter but that the youngster’s exploitation began only after Sheffield social services assumed parental control: “Something has to be done urgently to finally help Laura out of this nightmare and hopefully achieve some level of justice for all she has suffered. But no one seems bothered.”

Susan told the Observer: “My daughter is still a child, and yet they’ve all let her down so badly that she sees no way out. All the time she was in care I was told they were keeping her safe, when it was obviously the exact opposite. And now she’s at [the psychiatric hospital] they seem to just be waiting for her to kill herself. I’m terrified for her.

“All she wants to do is cut herself or take overdoses. She’s said her goodbyes to us, she’s desperate to die. I’m just waiting here expecting someone to knock on my door to tell me she’s been found dead.”

Sheffield city council was asked to comment on a number of specific allegations relating to its dealings with Laura, but declined to do so. John Macilwraith, the council’s executive director for people services, said staff always acted when alerted to cases of child sexual abuse.

The psychiatric hospital similarly declined to comment.

South Yorkshire police said that a coordinated investigation was under way in relation to Laura.

A spokesman added: “As part of this, hundreds of documents have been compiled and reviewed, multiple witness accounts have been taken, a number of searches have taken place and a total of 13 people have been arrested.

“Enquiries are ongoing. In the meantime we are working with our partners to ensure the victim is continuing to get the support and specialist care she needs.”

It is understood that the 13 people arrested were released on conditional bail.

* Names have been changed