Staff at a women's prison could face disciplinary action after a report into the deaths of six inmates in 12 months.
The report found a "lack of communication" among some staff
Prisons Ombudsman Stephen Shaw has criticised Styal Prison in Cheshire for its handling of an inmate's death.
A report said it took more than an hour for an ambulance to be called for Julie Walsh, who had taken anti-depressants.
Among the recommendations, it said the Prison Service should consider whether disciplinary proceedings would also be justified in the cases.
It called for action after finding prison staff did not stop prisoners stealing dangerous medicines.
The report, published on Thursday, followed an inquiry into the deaths of inmates at the jail.
The women were vulnerable and many had a history of drug abuse and, in some cases, unstable living arrangements or mental health problems, said Mr Shaw.
But failures by staff had contributed to the deaths, he added.
A four-page summary and action plan from Mr Shaw's report were published in January by the then prisons minister, Paul Goggins.
Ms Walsh died in August 2003 after taking an overdose of the stolen drugs and had begun convulsing and bleeding. She was unconscious by the time an ambulance was called.
The nurse who attended believed she was having an epileptic seizure.
Sarah Campbell died at Styal Prison after taking anti-depressants
Four other women who took pills from the stolen bottle were taken to hospital by ambulance and later discharged.
The report praised many staff for their actions on the night Ms Walsh died.
But it said staff who discovered the stolen medicine bottle did not report it and instead threw it in a bin.
The ombudsman's report criticised a lack of communication between medical and non-medical staff over the deaths of five other inmates.
The report comes after an inquest jury found that the prison had failed its in "duty of care" in relation to the death of 18-year-old Sarah Campbell.
She died at Styal after taking anti-depressants in January 2003.
The ombudsman said there was "inadequacy of the regime and procedures" in place at Styal at the time, particularly on the jail's Waite wing where five of the six deaths occurred.
Mr Shaw made a number of recommendations to improve the care of vulnerable prisoners, particularly in the period immediately after their arrival at the jail.
A Prison Service spokesman said: "We welcome this report, which has made a valuable contribution to suicide prevention not just at Styal but throughout the women's estate.
"Many important changes have been made at Styal in the intervening period, including the new first night centre and the appointment of a dedicated suicide prevention co-ordinator."
The independent organisation Inquest, which works with families of those who die in custody, said the report failed to reflect any evidence that arose from the inquests into the six deaths at Styal.
Co-director Deborah Coles said the government's response failed to address why it failed to implement a recommendation made in 2002 that "as a matter of urgency a proper detoxification regime should be put in place".
An inquiry was needed to look at sentencing, treatment and the care of vulnerable women in addition to allowing "meaningful participation of bereaved families", she added.