Four police officers present when a black former paratrooper choked to death in a police station nearly eight years ago were guilty of the "most serious neglect of duty", the police watchdog said today.

The treatment of Christopher Alder amounted to "unwitting racism", said Nick Hardwick, the chairman of the Independent Police Complaints Commission (IPCC).

In a damning 400-page report, Mr Hardwick condemned the behaviour of the four officers as "disgraceful" and criticised the two police investigations into Mr Alder’s death in Hull on April 1 1998.

Mr Hardwick also called on Tim Hollis, Chief Constable of Humberside Police, to make an immediate and unreserved apology to Mr Alder’s family. His findings were rejected "in the strongest terms", however, by the former Deputy Chief Constable in charge of disciplinary matters in the force at the time.

Mr Alder, of Dagger Lane, Hull, banged his head during a scuffle outside a city centre hotel. He was taken to Hull Royal Infirmary for treatment and was then arrested for an alleged breach of the peace.

He choked to death on his own blood and vomit as he lay on the floor of the police station without moving for 11 minutes. A controversial BBC TV programme showed CCTV footage taken in the police station of Mr Alder dying with his trousers around his ankles.

Mr Hardwick said: “I believe the failure of the police officers concerned to assist Mr Alder effectively on the night he died were largely due to assumptions they made about him based on negative racial stereotypes.

“I cannot say for certain that Mr Alder would have been treated more appropriately had he been white - but I do believe the fact he was black stacked the odds more heavily against him.”

Five officers were cleared of Mr Alder’s manslaughter and misconduct in 2002, even though an inquest had concluded that he was unlawfully killed. At least four have now retired.

Mr Hardwick said: "The most serious failings were by the four police officers who dealt with Mr Alder throughout his time in the custody suite. I believe they were guilty of the most serious neglect of duty.

"I do not believe, as has been alleged by some, that any of these officers assaulted Mr Alder. Nor can it be said with certainty, such are the contradictions in the medical evidence, that their neglect of Mr Alder, as he lay dying on the custody suite floor, caused his death. However, all the experts agreed that, at the very least, the officers’ neglect undoubtedly did deny him the chance of life."

He added: "There is no excuse. Far from being typical of most police officers, their behaviour has disgraced police officers and the police service as a whole. Their failures were personal and individual."

Gordon Clark, former Deputy Chief Constable of Humberside Police, was the officer responsible for disciplinary matters in the force at the time of the death of Mr Alder. In a statement today, he rejected "in the strongest terms" the criticism of him contained in the IPCC report, and said that he suspected that the IPCC had an "agenda from the outset".

He said: "The criticism is not supported by the facts, it is at best opinion. At no time did I obstruct the disciplinary process.

"This was a tragic and serious matter. My job was to consider the culpability of the officers involved. My decisions were at all times based on my professional judgment and assessment of the circumstances leading up to Christopher Alder’s death and I stand by the decisions I made at the time.

"Christopher had been drinking and had been involved in a fight. He was taken to hospital for treatment. Police officers attended at the hospital. He was extremely disruptive at the hospital but was eventually examined by a doctor and certified as being fit to be detained by the police.

"Those who have since examined this tragic incident and have viewed the CCTV tapes have known what the awful outcome is before viewing them. Unfortunately, the police officers did not and could not have realised the seriousness of his condition.

"I fully acknowledged from the outset when considering the disciplinary matters that the custody sergeant had neglected his duties. All of the officers faced a disciplinary hearing.

"At no time did the Police Complaints Authority express any concerns about my conduct of the disciplinary process and at all times I acted within my legal powers."

He said: "The IPCC criticism is not, I believe, evidence-based and this causes me to suspect that they have a certain agenda from the outset, especially given that the criticism was drawn up before they even condescended to speak with me. I sincerely regret that Christopher died while in the custody of Humberside Police but totally reject the criticisms made of me."

Earlier, Alder's sister, Janet, told BBC Breakfast that the police officers acquitted of his manslaughter had never publicly answered a question over the incident in eight years.

"I’m hoping the IPCC have got hold of these police officers and we now hear their version of what happened that night," she said. "I would like to see a public inquiry into how all the bodies have dealt with it."

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