DRUGS worth an estimated £40,000 were found at a "very unsafe" prison, an inspection report has revealed.
Security searches also led to the discovery of 350 litres of illicitly-brewed alcohol known as "hooch" at HMP Garth over the Christmas period.
The training prison near Leyland holds over 800 adult males, including prisoners from East Lancashire.
HM Inspectorate of Prisons said levels of violence at the jail had increased "substantially" with many incidents linked to drugs, gangs and debt.
Assaults on staff had also risen, while dozens of prisoners were held separately because of fears for their safety.
Drugs including substances previously known as legal highs have been identified as a major factor in the wave of violence that has swept across jails in England and Wales.
The watchdog did find Garth had made real progress in work to rehabilitate prisoners.
Chief Inspector of Prisons Peter Clarke said: "This was an unusual inspection of contrasting and conflicting outcomes.
"The progress in rehabilitative work was real and speaks to the potential this establishment has.
"The prison was, however, one of the most unsafe we have been to in recent times. Violence and drugs dominated the prisoner experience."
Michael Spurr, chief executive of HM Prison & Probation Service, said: "As the Chief Inspector points out, there is much good work being done at HMP Garth but the deterioration in safety is a serious concern and reversing this is the top priority.
"An experienced senior management team has been appointed to work alongside a new governor to help drive progress over the coming months.
"This will be supported by additional staffing and resources and an improvement plan, which is already in place to address the issues raised in the report."