Neglect and a series of gross failures by the Home Office and other agencies contributed to the death of a vulnerable Ghanaian man from hypothermia, dehydration and malnutrition, an inquest jury has found.

In a damning narrative conclusion, the jury found that Prince Fosu, a car parts dealer, had died suddenly after developing these conditions while he was suffering from psychotic illness.

The jury criticised many aspects of the healthcare systems in Harmondsworth immigration removal centre (IRC) at the time of Fosu’s death and said there were “gross failures across all the agencies”.

They found that Home Office staff failed to spot and respond to Fosu’s deteriorating condition and failed to monitor their contractors adequately.

Speaking after the inquest, Fosu’s father, Prince Obeng, welcomed the jury’s conclusions. “The jury have done their job,” he said. However, he added, “everyone at every level at Harmondsworth” had failed his son.

Fosu, 31, from Ghana, died at Harmondsworth IRC near Heathrow on 30 October 2012. After six days in segregation, he was found naked and without bedding in a cell peppered with debris. He had been suffering from psychosis. Malnutrition, dehydration and hypothermia contributed to his death.

Checks on his wellbeing every 15 minutes at Harmondsworth showed no evidence that he had eaten, drunk or slept over his six days there.

He was seen lying naked on a cold concrete floor, in unsanitary conditions, behaving “bizarrely”, not communicating with anyone and with no bedding or mattress.

During the inquest hearing, a member of the Independent Monitoring Board, Tony Smith, told the jury: “Mr Fosu died in plain sight. We let him down big time.”

As well as the IMB, other interested parties in the case before the coroner Chinyere Inyama included the Home Office, contractors Mitie and GEO, and the chief constable of Northampton police. Three doctors, Wesley Joseph, Anna Sharif and Kirpal Singh, face a review of the way they cared for Fosu by the General Medical Council.

The jury criticised GEO for removing Fosu’s mattress and bedding when they held him in segregation, saying it was indicative of a “casual approach” to his welfare. Doctors showed insufficient professional curiosity about his condition and the IMB failed to monitor the situation effectively, they added.

The jury found that control points put in place to protect vulnerable detainees were grossly ineffective.

Fosu entered the UK on a valid business visitor visa. He was then refused leave to remain on entry but appealed. He was booked on a flight to leave Britain on 5 November 2012.

On 21 October, he was arrested as he ran down the road naked in Kettering and was detained in Corby police station for three days. A check on his immigration status found he had overstayed his visa. Despite police officers’ concerns, a mental health assessment in Corby police station concluded Fosu was fit to be detained and on 24 October 2012 he was transferred to Harmondsworth IRC.

In detention Fosu was found ranting into a mirror. He was then restrained and put into segregation shortly after his arrival where he remained until his death six days later.

During the period of segregation he lost 15% of his body weight, going from 55kg (8st 9lb) to 47kg (7st 6lb). He was found to have died of cardiovascular collapse with psychosis, malnutrition and hypothermia.

Prince Fosu’s father, Prince Obeng, said his son was a quiet and obedient man who had never previously experienced comparable episodes of ill health. “I never knew that things like this could happen in Europe,” he said. “The Home Office has not been in touch with me but I would like them to apologise for their failure to protect Prince.”

He criticised the time it had taken for the inquest to be held: “When Prince came to the UK for a visit his daughter was just one year old. Now she is eight.”

The prisons and probation ombudsman (PPO) recommended the Home Office refer three doctors to the General Medical Council.

Sue McAllister also recommended that the Home Office investigate the actions of Home Office staff who were responsible for monitoring Fosu’s care in the segregation unit and that disciplinary action should be considered.

McAllister said: “I very much regret that the lengthy delay will inevitably diminish the impact of this (PPO) report and make it more difficult to hold those involved properly to account.

“This is a very troubling case. Mr Fosu spent six days at Harmondsworth, and apart from his first few hours, he spent his time segregated, living naked in a room dirty with faeces, urine and uneaten food, without a mattress or bedding. He did not eat for much of this time and rarely engaged with staff.

“I am particularly troubled that Mr Fosu lived in an unfurnished room without proper justification or review, which I consider to be inhuman and degrading. I consider that IRC managers were responsible for a culture which I can only describe as uncaring.”

The PPO acknowledged that managing Fosu’s complex and difficult behaviour presented staff at Harmondsworth with challenges. However, she added: “We consider that the care he received fell considerably below acceptable standards.”

A Home Office spokesperson said: “The standard of care Mr Fosu received was unacceptable, and we must never allow this to happen again.

“Since Mr Fosu’s death we have increased the number of staff in immigration removal centres, improved how detainees are managed and safeguarded, including the introduction of the Adults at Risk policy and increased monitoring of vulnerable people in detention.”