A prison in Kent has been heavily criticised over a drugs culture, dirty and untidy facilities and a lack of training opportunities for inmates.
Maidstone Prison can hold nearly 600 inmates
A prisons inspectorate report said issues at HMP Maidstone were compounded when overcrowding led to the reopening of a wing deemed "unfit for purpose".
Nearly half of inmates said drugs were common. Food facilities were of a state that would see a restaurant shut down.
Prison bosses have been ordered to draw up an action plan to address failings.
Anne Owers, chief inspector of prisons, said: "HMP Maidstone is an overcrowded, dilapidated Victorian prison... [with] a number of failures in basic hygiene, cleanliness and decency for which there is no excuse."
Of the "unfit for purpose" unit being brought back into operation, Ms Owers said: "The entire wing had to be used because we need every prison cell we can lay hands on.
"When a system is under such pressure, just keeping the show on the road takes a lot of effort and energy and people sometimes take their eye off other important things."
She said one in five inmates were "unemployed and unoccupied and that's simply not good enough for a training prison".
Some newly-arrived prisoners were left without pillows or clean underwear.
Referring to the cooking facilities, Ms Owers said: "The kind of things we found, if you had them in a health and safety inspection for a restaurant, you wouldn't be able to be open until it had been sorted and cleaned."
She concluded: "If we keep prisoners in squalid and unhygienic conditions, if we don't provide them with enough activity and skills, if it's still too easy to get hold of drugs - then prison isn't going to make a blind bit of difference to them."
The Prison Service said work was under way to improve and upgrade facilities, more work and skills places would be introduced, and the drugs problem would be addressed with police involvement and mandatory testing.
An unannounced re-inspection will be carried out to ensure the report's recommendations are implemented.