Bedford Prison in special measures over safety concerns
Bedford Prison has been placed in special measures, according to the Prison Officers Association (POA).
Spokesman Martin Field said an "exodus of experienced staff" had meant violence at the prison was now "an everyday occurrence".
He added the prison service had not learned the lessons of a riot in November 2016 which caused £1m of damage to two wings.
The Ministry of Justice said the jail "needs additional, specialist support".
Attacks on staff
The Category B prison holds more than 500 male prisoners, although capacity is thought to be about 320.
In the last 18 months the prison has been dogged by controversy, including several attacks on staff.
A report by the Independent Monitoring Board also revealed the government had been warned of "an alarming decline in safety" at Bedford two months before the 2016 disturbance.
The POA has written a letter to the government's legal department, setting out their concerns over management failings and safety at the prison.
Mr Field said putting the prison in special measures was "a sad day for the people who work there".
He said failed government policies had led to "a mass exodus of experienced staff, which was the catalyst for an escalation of violence".
"Until the prisoners can see that the establishment is being run properly, their only outlet is violence," he said.
"A lot of the symptoms that caused the riot are still prevalent today."
Pressure on brain
He said one prison officer recently had to have emergency surgery to relieve pressure on his brain after a serious assault by an inmate.
"Violence is an everyday occurrence, sometimes severe," he said.
"A once-proud prison a few years ago, high-performing - has now been reduced to this level."
A Prisons Service spokeswoman confirmed the prison had entered special measures, adding: "it simply means HM Prisons and Probation Service has determined it needs additional, specialist support to improve performance."