Eighteen-year-old Tuan Ho was found hanging in his cell at HMP Chelmsford on Monday evening.
Penelope Gibbs, director of the Prison Reform Trust’s Out of Trouble programme, said: "It is a tragedy when a teenager takes their own life in the care of the state. Even more so when that teenager has been accused of a non-violent crime and has not even been sentenced.
"To prevent this waste of young lives we must ensure remand is used more sparingly and that regimes are more nurturing."
The Prison Service said in a statement: "HMP Chelmsford prisoner Tuan Ho (dob 21/10/92) was found hanging in his cell at 7:16pm on Monday 4 July. Staff attempted CPR and paramedics attended but he was pronounced dead at hospital at 8:15pm.
"As with all deaths in custody the Prisons and Probation Ombudsman will conduct an investigation."
Ho is the seventh teenager to die in custody so far this year. In May CYP Now revealed that five teenagers died in custody in the space of less than five weeks this year between the beginning of March and mid-April. A sixth died in Belfast's Hydebank Wood Young Offenders Centre on 4 May.
News of the deaths led to calls for an independent review of the youth secure estate.
The death at HMP Chelmsford comes three and a half years after another 18-year-old took his life at the establishment.
Sudanese national Joker Idris was found hanging in his cell on Christmas Day 2007, while nearing the end of a six-month prison term for affray.
The previous day he had been told that he was to remain in custody at the end of his sentence before being deported back to Sudan.
