Prison staff have become "inured" to conditions in jails that are unacceptable in 21st century Britain, a watchdog has warned.
In a scathing critique, Chief Inspector of Prisons Peter Clarke said drugs and violence remain rife across much of the estate in England and Wales.
He highlighted how thousands of inmates are living in "squalid" and overcrowded cells, locked up for nearly 24 hours a day.
Publishing his annual report for 2017/18, Mr Clarke said: "I have seen instances where both staff and prisoners alike seem to have become inured to conditions that should not be accepted in 21st century Britain.
"Terrible conditions that people seem to have lost the ability to recognise as not being good but also as not being bad. It's just become the normal."
He said that over the year HM Inspectorate of Prisons documented some of its most disturbing ever findings.
Inspectors at the rat-infested HMP Liverpool could not recall encountering worse conditions, HMP Nottingham was found to be "fundamentally unsafe" and the iconic Wormwood Scrubs had seemingly "intractable" problems.
Mr Clarke criticised the "disappointing failure" of many establishments to act on his office's previous recommendations.
The chief inspector said it was "noticeable" that a huge increase in violence across the prison estate had taken place at a time when large reductions in staff numbers were taking effect.
He welcomed efforts to boost staffing levels and the introduction of the "urgent notification" process, which allows the inspectorate to demand immediate action from the government to address major failings at individual jails.
But Mr Clarke said there was still a "huge amount" to do to reverse the decline in treatment and conditions in some facilities.
His review also:
-Flagged up the "shockingly" high numbers of inmates who acquire a drug habit behind bars, noting that surveys showed 13% of adult men reported developing a problem with illicit drugs after they arrived
-Questioned why it had taken so long to adopt new technology to tackle smuggling of contraband such as drugs and mobile phones
-Found safety declined in 14 jails inspected in 2017/18, while nine showed improvement
-Detailed sometimes "dramatic" increases in violence behind bars, including rises in assaults on staff
-Said around half of prisons had too few places for the population
Mr Clarke said: "I realise that in recent years many prisons, short of staff and investment, have struggled to maintain even basic standards of safety and decency.
"Some prisons, in very difficult circumstances, have made valiant efforts to improve. Others, sadly, have failed to tackle the basic problems of violence, drugs and disgraceful living conditions that have beset so many jails in recent years."
Justice minister Rory Stewart said the Government had listened carefully to Mr Clarke's recommendations.
"That is why we are putting £16 million extra into cleanliness and decency and £7 million for in-cell telephony," he said.
"We are also investing £14 million into tackling organised crime, and installing new technology like body scanners which will help to make our prisons drugs-free.
"Meanwhile, our new education and employment strategy will ensure more prisoners learn a trade while inside and find a job on release.
"Underpinning all of this are over 3,000 extra prison officers we've recruited in the last 18 months to help keep prisoners safe and turn their lives around."
Michael Spurr, chief executive of Her Majesty's Prison & Probation Service, said: "Many prisons have had a challenging 12 months and whilst the Inspectorate has recognised particularly acute problems in a number of prisons I am pleased that they have also recognised the progress and good outcomes in others."
Labour claimed the "crisis" in prisons has now become an "emergency".
Shadow justice secretary Richard Burgon said: "The Government must now take responsibility for some of the worst prison conditions that inspectors have ever seen."