An 84-year-old immigration detainee suffering from dementia and declared unfit for detention died in handcuffs, a report has revealed.
HM Inspectorate of Prisons (HMIP) compiled the report after visiting Harmondsworth immigration removal centre, near Heathrow airport.
Inspectors condemned "shocking cases where a sense of humanity was lost" at the centre in west London.
The Chief Inspector of Prisons said some services were "poorly managed".
The Prison Reform Trust said the centre had "forgotten the basic principles of humanity and decency".
HMIP inspectors compiled the report after an unannounced visit to the centre last August.
The 84-year-old was taken to hospital in handcuffs and he died while still in restraints, inspectors found.
Doctors said the Canadian man was unfit for detention or deportation after diagnosing him with Alzheimer's disease, but he was not released and no referral was made to social services.
Medical notes described him as "frail, 84 years old, has Alzheimer's disease ... demented. Unfit for detention or deportation. Requires social care".
He had been in handcuffs for almost five hours when he died, the report said.
The Prisons and Probation Ombudsman is preparing to investigate his death and inquest proceedings are being conducted by West London Coroner's Court.
Other examples in the report included a stroke victim in a wheelchair, who was handcuffed on a journey to hospital for no obvious reason and a dying man who remained handcuffed while sedated and undergoing an angioplasty procedure in hospital.
Ministers have pledged to scrutinise more closely the performance of the private contractor GEO Group UK Ltd, which runs Harmondsworth.
The group also runs Dungavel House immigration removal centre in South Lanarkshire.
The UK Border Agency's website says "removal centres are used for temporary detention, in situations where people have no legal right to be in the UK but have refused to leave voluntarily."
"Those detained in any of our centres can leave at any time to return to their home country," it adds.
"Some detainees are foreign national prisoners who have completed prison terms for serious crimes, but who then refuse to comply with the law by leaving the UK."
However inspectors said 11 detainees had been held at the centre for more than a year, including a man who had been held for more than two years despite being willing to return to his own country.
There were also nearly 100 hunger-strikers identified in the six months prior to the inspection and HMIP described some of the rooms at the 600-capacity detention centre as overcrowded, dirty and bleak.
Juliet Lyon, from the Prison Reform Trust, said: "Have the authorities responsible for Harmondsworth forgotten the basic principles of humanity and decency that must apply to any form of custody?"
Chief Inspector of Prisons Nick Hardwick said: "These were truly shocking cases, and they weren't isolated, and they reflected a culture where too often the individual human needs of the people who were being held were simply being forgotten.
"And in the worst case, this frail, elderly Canadian gentleman with dementia died in the most undignified and disgraceful circumstances possible."
He added there was a feeling Harmondsworth was in "a state of drift" with concerns about its future management, as the current contract was under review.
"The centre did not seem to be progressing and some services were being poorly managed," he said.
"Most importantly, there needed to be a refocusing on individual needs of the most vulnerable people in detention, some of whom had been utterly failed by the system."
The report said on at least two occasions, inspectors discovered elderly and vulnerable detainees were "needlessly handcuffed in an excessive and unacceptable manner".
Immigration minister Mark Harper said the use of restraint in the case of the dementia sufferer seemed "completely unjustified and must not be repeated".
"Clearly, performance by the contractor running Harmondsworth has been below the high standard expected," Mr Harper said.
"This report makes a number of recommendations that we will be taking forward and I expect to see significant improvement."
Shadow Home Secretary Yvette Cooper said: "This shocking report exposes incidents of inhumanity."
"Terminally ill, dying elderly people should not be handcuffed to their hospital bed.
"People will rightly be appalled by this incident and the home secretary should be appalled too."
In a statement Harmondsworth contractor GEO said: "Detainees are not routinely handcuffed when taken out of the centre.
"However, where there is a documented risk of absconding, handcuffs may be used, balanced against a number of factors, including their age.
"Managers have to use discretion to take difficult decisions and we have issued them with additional guidance."
The contractor added that GEO Group UK Ltd had an "excellent track record" of providing services as evidenced in other recent reports by the HMIP.