Conditions inside Suffolk's Highpoint Prison have been criticised as "squalid" in a report out Wednesday.
An investigation by the Independent Monitoring Board revealed that too many inmates were forced to share a cell and healthcare was not up to standard.
It said sharing single cells is degrading for inmates and unacceptable.
A Prison Service spokesman said a new induction unit should alleviate doubling-up and five new healthcare staff have been appointed.
The difficulties are partly blamed on staff shortages and the lay-out of the prison which is near Haverhill.
"Due to population pressures, it is sometimes necessary to double up prisoners in single cells, a prison spokeswoman said.
"However, the new induction unit at HMP Highpoint will minimise the amount of time that prisoners will spend in shared accommodation.
"Mental health provision has also improved considerably in the last 12 months.
"There are now weekly visits from a consultant psychiatrist as well as a mental health in-reach team," she added.
The report says that overall the prison has had a "good year".
In terms of general standards the prison scored 85% and security 82%.
In the last inspection in 2002 over 200 recommendations were made whereas this year there are only 57.