Women are being detained in a colonial-era men's jail because of overcrowding, as the NSW prison population passes 11,000 for the first time.
The Bathurst prison, classified as a medium-security men's jail, has been holding female offenders since January, documents obtained under freedom-of-information laws show.
The Dillwynia women's prison has regularly exceeded its operating capacity this year. Between seven and 10 female offenders are now being housed each week at Bathurst, the documents show.
Inspector of Custodial Services John Paget, who was appointed in October, has handed the NSW government a scathing report on systemic problems caused by overcrowding. The prison population reached 11,021 last month.
Dr Paget, a former chief executive of corrective services in South Australia, said the NSW prison system was harsh, austere and risky.
Praising the efforts of prison staff, he said policy decisions had led to overcrowding and it was ''remarkable'' that prisoners made it through each night safely.
The prisoners had the lowest daily hours out of cells of any state (7.8 hours compared with a national average of 10 hours) and NSW spent the least dollars per prisoner.
''Harsher conditions, including overcrowding … are strongly associated with serious prisoner misbehaviour and violence,'' his report said.
Last month, the Bureau of Crime Statistics warned that the rapid 13 per cent growth in NSW prisoners in the past 18 months was ''a matter of significant concern''.
Shadow attorney-general Paul Lynch said the government's administration of prisons was chaotic.
''It's at crisis point,'' he said. ''Sending women prisoners to a 19th-century men's prison shows the government has no idea what it's doing. The government have let this problem develop and paid no attention.''
A Corrective Services spokesman said they were capable of dealing with the prison population rise and were ''continuously reviewing'' bed occupancy and adjusting the use of space within prisons. He said women had been accommodated at Bathurst since the 1990s and most were in transit to courts or other centres and held in a separate area to men.
However, the Correctional Services website describes Bathurst as a men's prison and Corrective Services Commissioner Peter Severin did not include Bathurst in a list of women's prisons supplied to a parliamentary inquiry in 2012.