The discoveries were made during an unannounced visit to HMP Bristol in Horfield, earlier this year.
Nick Hardwick, the chief inspector of prisons, said a "sense of drift" had returned to the prison following a positive report in 2010.
The National Offender Management Service said the prison will receive support to help raise performance.
At the last inspection in 2010, Her Majesty's Inspectorate of Prisons had noted improvements and described a well-led prison with a "clear sense of direction" but found this progress had not been sustained.
The recent inspection found staff at the category-B prison, which can hold up to 600 inmates, were too "dismissive" towards inmates.
The report said staff displayed "delinquent" behaviour such as using "derogatory and abusive" language, and fewer prisoners than at similar prisons said staff treated them with respect.
Cells were also found to be dirty with damaged or missing furniture, offensive graffiti and an "infestation of cockroaches".
The report also noted a lack of clean clothes and adequate bedding for inmates.
And inspectors witnessed the "arbitrary punishment" of a prisoner when a prison officer stopped him from having his full meals.
The report said the prison has taken action to discipline the staff concerned.
Mr Hardwick said the experience of prisoners was "poor" and identified priorities for the prison to improve the environment and staff culture and "ensure prisoners have something useful to do that will equip them for the future".
Positives identified by the inspectors included broadly proportionate security procedures, and the prison largely meeting its resettlement challenges.
Michael Spurr, of the National Offender Management Service, said at the time of the inspection, the prison had been through a "significant period of restructure and change".
He also said a high turnover of prisoners presented "a challenging time for the governor and her staff".
"The prison and its staff will receive the support necessary to help raise performance and deliver a safe and constructive environment for the prisoners it holds," he added.
The governor of HMP Bristol, Andrea Albutt was unavailable for comment.
Staff verbally abused inmates and dirty cells were found at a Bristol prison, an inspection report has revealed.