William Pasquale, who has learning difficulties, was found with a makeshift noose around his neck in his cell at Feltham Young Offenders Institute, Middlesex, where four boys have already committed suicide.
His suicide attempt came just hours after he arrived at the prison to serve a two-month sentence following an incident with a stolen car.
Last night penal reform campaigners condemned the Prison Service for refusing to release the teenager on compassionate grounds - especially as he only has a few days left to serve of his sentence.
Police investigating the incident, which happened last month, are treating it as "suspicious". The prison is also conducting its own internal inquiry.
The boy's solicitor had warned that William was at risk because it was his first offence and prison would be his first time away from home.
However, he was sent to Feltham, the largest young offenders institute in Europe, and put in a cell with three boys.
He was found hanging from a sheet early the next morning and one of his cell mates was left to resuscitate him while they waited for a nurse to arrive.
Medical notes show that William suffered a cardiac arrest after his suicide attempt. He was taken to St Peter's Hospital in Surrey then transferred to St George's Hospital in Tooting.
Doctors advised that William, who was on a life support machine for several days, would possibly attempt suicide again and recommended he stay in the hospital.
However, prison guards came to take him away when he was able to stand up and talk again.
William has already made another attempt to harm himself and is now on 24-hour suicide watch in the health care centre at Feltham.
The Howard League, which campaigns for penal reform, is now taking Hounslow Council to court to force it to intervene.
"We feel for a full and independent investigation to be done, the local authority should intervene," said Fran Russell of the Howard League.
However, Hounslow Council says it does not have the legal jurisdiction to intervene.
Yesterday, a spokeswoman for the Prison Service said that it was not prepared to release the teenager because it could encourage inmates to harm themselves in order to obtain early release.Reuse content