The government is being warned it must take action to improve conditions at Bristol Prison, the BBC has found.
Inspector of prisons Peter Clarke is expected to issue an "urgent notification" letter to Justice Secretary David Gauke this week.
Inspectors visited the jail last week and gave it the lowest grading possible for safety and purposeful activity.
Facilities are described as "shocking and unfit for purpose" and there are concerns over "unreported violence".
The Category B prison, which currently holds about 520 prisoners, received the second lowest level grading for respect, and rehabilitation and release.
In January, Bristol's Independent Monitoring Board (IMB) said the jail had "shocking and unfit for purpose facilities and accommodation", and did not have enough staff.
'Lack of resources'
It said "unreported violence continues to remain a concern" and criticised the prison's "regular and ongoing inability to run a normal basic daily regime" blaming a "lack of resources".
It added it had not seen "any reliable data or evidence to enable it to conclude that prisoners are well prepared for their release".
The IMB wrote to then Prisons Minister Rory Stewart outlining its concerns.
It will be the fifth jail to be subject to the notification process since it was introduced in November 2017.
The other prisons to have received an urgent notification letter are Bedford, Birmingham, Exeter and Nottingham.
Under the procedure, the Justice Secretary has to publish an action plan to bring about immediate improvements.
A spokesman for the Prison Service said it was not able to comment at this stage.
HMP Bristol can hold 614 prisoners, mainly adult men and some young offenders.