A disabled prisoner was unable to wash properly for over a year because staff refused to carry him to the showers, a damning report revealed today.
Another disabled prisoner went six months without a shower because of a lack of staff "trained" to push his wheelchair, an official inspection found.
Inspectors said HMP Parkhurst on the Isle of Wight, where both men were held, lacked "basic levels of safety and decency".
Prisoners were poorly supervised by staff, violence was "endemic" and there was widespread abuse of prescription drugs.
It's claimed injuries to prisoners that were described as "unexplained" were not properly investigated, and a proper inquiry was not carried out into an alleged assault of a prisoner by a member of staff.
The report also found a group of radical Muslim prisoners were able to spread their extremist message to other inmates.
The Muslim chaplain who offered to set up a teaching group to combat the radicals received "little support" from management.
One group of staff were described by inmates as "intimidating", and inspectors overheard prisoners referred to as "bodies".
The category B prison, which holds nearly 500 mostly violent and sexual offenders, is a former military hospital first converted into a prison in the mid-19th century.
The report paints a picture of a dysfunctional institution. Parts of the prison building were dilapidated and litter dumped out of cell windows went uncollected.
Chief inspector of prisons Anne Owers said Parkhurst was a "troubled institution" with "substantial shortcomings".
She said relations between staff and management were "exceptionally poor".
The report said: "One prisoner with impaired mobility had not been able to shower for over a year, apparently for lack of staff support.
"Another who used a wheelchair was denied access to a basic regime and had not been able to shower for six months, apparently because only three staff were prepared to push his wheelchair and they had not been available to undertake this task."
Ms Owers said: "In many ways, Parkhurst is a failing prison: prisoners feel unsafe and poorly treated, and neither the environment nor the regime are suited to the role of a modern training prison.
"Exceptionally poor industrial relations also exert a malign influence over an already troubled institution."
"Parkhurst badly needs regional and national support to ensure the restoration of basic levels of safety and decency, together with investment to increase purposeful activity."
Phil Wheatley, director general of the National Offender Management Service, said he accepted the prison had fallen below an acceptable standard.
"Parkhurst now forms part of HMP Isle of Wight, whose Governor has embarked from May 1 this year on a radical programme of change with the help of a new senior management team."
"I am determined that the creation of the new prison and the associated restructuring will deliver the changes required," he said.
Juliet Lyon, director of the Prison Reform Trust, said today that she had called on the Prison Service to comply with its responsibilities under the Disability Discrimination Act.
She said she was writing to Director-General Phil Wheatley, Secretary of State Jack Straw and Trevor Phillips, chairman of the Equality and Human Rights Commission, to ensure the service does comply.
She said: "The Ministry of Justice is breaking the law by allowing Parkhurst and other jails to be used as an inhumane, double punishment for disabled people."