The remaining women prisoners in Durham jail should be removed as a matter of urgency, according to the Chief Inspector of Prisons, Anne Owers.
A report found women were held in alien and isolating conditions
Her call comes as an inspection report reveals there are high levels of distress among female prisoners.
A number of inmates were moved after a previous report recommeded the closure of the prison's women's unit, but six remain in worsening conditions.
Those six were due to leave by the end of the month, the Prison Service said.
Anne Owers said: "We commend the fact that most women were safely removed from Durham, following our last report.
"However, the few who remained were held in an even less suitable environment than the one we last inspected.
"The Prison Service has been made aware of the high levels of distress and real risk of suicide.
"Urgent action is required to ensure that women prisoners are no longer held in such isolated and alienating conditions."
Phil Wheatley, director general of the Prison Service, said: "The closure of the female unit at Durham was announced in May 2004.
"The majority of female prisoners had moved to other prisons by the end of last year."
He said a small number of women remained in a dedicated small unit, which was scheduled to close by the end of September 2005.
The female inmates would be transferred shortly but only when the accommodation they are moving to had been upgraded, he added.