Concerns about staff attitudes to inmates at Britain's largest prison were raised by the jails watchdog.
Chief Inspector of Prisons Anne Owers said nearly twice the average number of inmates complained of being victimised by staff at Wandsworth jail in south London.
Inspectors witnessed "poor behaviour" by staff, including an incident of "abusive language" to an inmate by a staff member during the team's four-day visit to the jail in July, Ms Owers' report disclosed.
The report, which made 160 recommendations for improvement, showed:
47% of all prisoners interviewed by inspectors said they had been victimised by staff, compared with the national average of 24%;
In the main prison, excluding specialist units, 52% said they had been victimised by staff;
Overall, 12% said they had been hit kicked or assaulted by staff - three times the average of 4%.
Black and Asian prisoners were more likely to report staff victimisation, and were over-represented in the segregation unit, it added. However, few race complaints resulted in action by senior managers at Wandsworth, a Category B local prison with 1,456 inmates.
Ms Owers said: "This is an inspection of an improving prison, but one which has a significant way to go before it is a good and well-performing prison. The most significant barriers to change are the constant and increasing population pressure, and the approach and attitude of some staff. Taken together, they pose a significant challenge.
"But the gains already made in some areas of the prison provide evidence of what can and what needs to be achieved."
