The death of the seventh teenager in custody this year has triggered calls for an independent inquiry into the imprisonment of young people which campaigners say needs a "complete overhaul".
Tuan Ho, 18, was found hanging in his cell at Chelmsford prison and young offender institution on Monday night and died later in hospital.
His death comes after five teenagers died in five separate institutions between 16 March and 18 April, including two who were on suicide watch. A sixth teenager died at Hydebank Wood young offenders centre and prison in south Belfast in May.
The deaths, all suspected suicides, have alarmed prison reformers and raised questions about the help available to vulnerable young people.
All seven deaths will be investigated by the Prisons and Probation Ombudsman, who is considering issuing urgent recommendations to the Prison Service and Youth Justice Board. Helen Shaw, co-director of Inquest, called for "decisive action".
"The youth justice system needs more profound scrutiny and there is an urgent need for a holistic inquiry in public to examine wider systemic and policy issues ... The failure of successive governments to hold such an inquiry runs counter to the spirit of accountability and the pressing need to learn from failures in the system that cost children and young people their lives," Ms Shaw said.
Juliet Lyon, director of Prison Reform Trust, said any review must examine why so many vulnerable young people end up in custody in the first place. Official figures show that there have been 150 teenage deaths in custody since 1990, including 32 under the age of 18.
The youngest to die this year was Ryan Clark, 17, who was found hanging in his cell at Wetherby young offender institution in West Yorkshire on 18 April. He, like Tuan Ho, was on remand.
It came the day after the death of Mahry Rosser, 19, who was serving three years in New Hall prison in Wakefield, West Yorkshire, for robbery. She died in hospital three days after she was found hanging in her cell.