Portsmouth, UK (CNN) The relatives of more than 450 patients who died after being over-prescribed drugs while in hospital have called for the British government to accept culpability for their deaths.

"There was a disregard for human life and a culture of shortening the lives of a large number of patients," the report said, adding that the hospital's policy of administering opioids was "without medical justification."

Ann Reeves' mother, Elsie Devine, was admitted to hospital to help her recover from a urinary tract infection, and was one of those killed while in the hospital's care. She died just four weeks after being hospitalized, and Reeves believes that it was the high doses of pain medication that were responsible.

"It would kill you, it would kill anybody," she told CNN. "She had no chance."

The report alleges that Jane Barton, a doctor and clinical assistant who visited the ward daily, was to blame for the hospital's drug policy. Over the course of 11 years, from 1989 to 2000, at least 456 people died after being given diamorphine -- synthetic heroin -- as a painkiller, under the direction of Barton, the report said.

The report found that another 200 patients potentially had their lives shortened by the drugs administered by nurses on the ward under Barton's direction.

Barton, who was found guilty of "serious professional misconduct" and censured for a failure of care of 12 patients between 1996 and 1999 but never prosecuted nor struck off the medical record, maintained that she had always prioritized her patients' interests.

"Throughout my career I have tried to do my very best for all my patients and have had only their interests and well being at heart," she said in a statement in 2010, according to the BBC. She retired soon after.

'I'm her voice now'

Wednesday's report, which claims the hospital, local and national authorities failed to act in ways that "protected patients and relatives," is a partial vindication for Reeves, who has spent 19 years searching for the truth.

But she says she won't rest until the government faces its role in the tragedy.

"I'm her voice now, and I will not stop, until someone in this government, in the Department of Health, can sit me down and say, 'this is why we gave your mother those drugs'."

On Wednesday, British Health Secretary Jeremy Hunt apologized "on behalf of the government and the NHS," for the deaths, referring to the country's National Health Service.

In a foreword to the report, the panel's chair, Rev. James Jones, said that relatives' attempts to find answers to the patient deaths "had been repeatedly frustrated by senior figures," and that their "anger is also fueled by a sense of betrayal."

Jones added that admitting a loved one to the care of medical professionals "is an act of trust and you take for granted that they will always do that which is best for the one you love."

"It represents a major crisis when you begin to doubt that the treatment they are being given is in their best interests. It further shatters your confidence when you summon up the courage to complain and then sense that you are being treated as some sort of 'troublemaker'," he said.

According to Reeves, health authorities took advantage of her mother's generation's trust in the medical profession.

"My mum came from a time when they though doctors were gods," she said. "They believed everything a doctor said. But the world has moved on now. We've got the internet, we've got the process of checking what drugs we have, and certainly for us, we will always be checking the medical file and making sure that we know what's going on."

The report references serial killer Harold Shipman, a British doctor who was found guilty of murdering 15 of his elderly patients, along with one count of forging a patient's will.

Despite only getting convictions for a handful of murders, an inquiry in 2002 found that he killed 215 of his patients over a 23-year period. Shipman dispatched his victims -- mostly elderly women -- with large amounts of diamorphine from 1975 to 1998, a report said.

Once, he used 12,000 milligrams of the drug to end the life of a terminally ill patient -- an amount that could kill over 300 people.

Shipman, confirmed as Britain's worst serial killer, took his own life in 2004 whilst in custody.