He found that children and young prisoners at the centre were left in "dilapidated, dirty and cold" cells with no blankets. Some had no access to showers. Others spent 23 hours a day in their cells, were forced to wash their clothes in their hand basin and were allowed only one set of underwear a week.
"The core of the institution was rotten," said the Chief Inspector in his report: "I ask the staff at Feltham and Prison Service Headquarters implicated by these remarks whether they would be happy for their sons, or the sons of any of their friends, to be on the receiving end of the treatment and conditions described in the report, which are unacceptable in a civilised country."
It emerged yesterday that the governor of Feltham, Clive Welsh, has been given a promotion and will next month become a senior civil servant at the Home Office. Mr Welsh said that his move to the finance division of the Home Office was unrelated to Sir David's findings and that he had been in line for promotion for three years.
Sir David, who said the report was "without doubt, the most disturbing that I have had to make during my three years as HM Chief Inspector of Prisons", was clearly angry that 187 recommendations he made after an inspection of Feltham two years ago had largely been ignored.
Conditions and treatment at Feltham are, Sir David said: "in many instances worse than when I reported on them two years ago and reveal a history of neglect of those committed to their charge".
He was especially concerned by the treatment of youngsters with mental health problems in Feltham's healthcare centre.
Yesterday, Richard Tilt, the director general of the Prison Service, visited Feltham in his last official appointment before retiring. He accepted the "very serious criticisms" and said an extra pounds 6.5m would be added to Feltham's pounds 17m budget to improve conditions.
Young prisoners talked yesterday of the squalor in which they lived. One 16-year-old remand inmate said: "Everyone gets scabies from the mattresses, which are covered in blood. The cells have got food all up the walls and the showers are always breaking." Inmates said new mattresses and bedding had been delivered yesterday in advance of the arrival at Feltham of reporters and television cameras.
There are 922 children and young prisoners at Feltham, including 31 15-year-olds. In his report, the Chief Inspector called on the Prison Service to set up a new young offender centre on the east side of London, to relieve the "intolerable pressure" on Feltham.
Sir David said that about a quarter of inmates reported, on arrival, that they had used crack cocaine but no detoxification programme was available. Inside the residential units, youngsters had to eat their meals in their cells, sitting alongside "filthy toilets".
Many of the prisoners stayed in bed asleep for much of the day. Sir David quoted one 16-year-old boy who said: "I have nothing to do. If I get depressed, I talk to the chaplain and ask him to pray for me. Most of the time I sleep."
The Chief Inspector also referred to another prisoner who had woken up to find his cell mate trying to hang himself. The prisoner supported his cell mate's body until staff arrived to cut him down and take him for medical treatment. Sir David said: "The young man himself remained in that cell. No one talked to him, no one counselled him. No one subsequently gave him work on the unit to enable him to get out of that cell. He had not been given a replacement cell mate, despite asking for one and so remained alone."