The smell of dead rats made working conditions at a prison “unbearable”, a report has said.
Rodents’ bodies were in the foundations of HMP/YOI Portland, the prison’s Independent Monitoring Board (IMB) found.
Its annual report said rats’ bodies were stored in a shed after a “big operation” to address the problem.
The Prison Service said it had taken “immediate action”, including “refurbishing all residential units”.
Stairwells and shared areas of the jail were “never cleaned” and “often littered with food”, IMB inspectors found.
The report said: “One member saw dead rats stored in a shed on the grounds and for some weeks working conditions in the administration building (including the IMB office) were unbearable due to the smell of dead rodents in the foundation cavities.”
It said the rat problem had persisted despite the operation to deal with them.
It also found some inmates of the category C prison, which was originally built in 1848, were kept in “dingy, insanitary, overcrowded and unhealthy” cells.
“It cannot be beyond the means of the Prison Service to ensure that windows fit properly and will close and open, that the mould problem is dealt with,” the report said.
Margaret Melhuish, from IMB Portland, said a lack of space, ventilation and screens for toilets was “inhumane”.
“On older wings, prisoners share cells originally built for one prisoner which are very small,” she said.
“A prisoner on the lower bunk has his head next to the toilet with no screening.”
The report said the jail, which holds 530 adult prisoners and young offenders, had some “frustrated prisoners” who had vandalised cells and plumbing.
One area had been flooded six times, wrecking electrical equipment and documents, the IMB said.
“Operational staff were exasperated and demoralised,” the report added.
The report also criticised the prison’s shortage of mental health staff and the “large number” of inmates being released into homelessness.
However, the IMB said “significant improvements” had been made to the jail’s approach to managing “complex offenders” and “self-isolating prisoners”.
In a statement, the Prison Service said: “Immediate action has been taken at HMP Portland including refurbishing all residential units.
“We work closely with local authorities to identify offenders who are at risk of sleeping rough and have launched a £6 million scheme that will help them stay off the streets and away from crime.”