The UK government has apologised to relatives of hospital patients who died as a result of being given life-shortening opioid drugs without medical justification and said criminal charges could follow.

An independent inquiry, published on Wednesday, found that 456 patients died and possibly 200 more had their lives shortened because of the routine practice at Gosport War Memorial Hospital.

In a statement after prime minister’s questions, the health and social care secretary, Jeremy Hunt, described the inquiry’s findings as deeply troubling and said there had been “a catalogue of failures” by the local NHS, the police, the coroner, and the Department of Health (now the Department of Health and Social Care).

He said: “Nothing I say today will lessen the anguish and pain of families who have campaigned for 20 years after the loss of a loved one, but I can at least on behalf of the government and NHS apologise for what happened and what they have been through.

“Had the establishment listened when junior NHS staff spoke out, had the establishment listened when ordinary families raised concerns, instead of treating them as troublemakers, many of those deaths would not have happened.”

He said the police working with the Crown Prosecution Service and clinicians would consider whether criminal charges should be brought. Hunt suggested that Hampshire constabulary should consider whether the investigation should be conducted by another force given its “vested interest”.

Earlier, in response to a question at PMQs, Theresa May offered her own apology for the length of time bereaved relatives have had to wait.

She said: “The events at Gosport Memorial hospital were tragic, they are deeply troubling and they led to unimaginable heartache for the families concerned … I am sorry that it took so long for the families to get answers from the NHS.”

The inquiry, led by the former bishop of Liverpool James Jones, concluded that Dr Jane Barton, the GP who ran wards at Gosport War Memorial hospital, routinely overprescribed drugs for her patients in the 1990s. Consultants were aware of her actions but did not intervene.

The panel said concerns were raised as early as 1988, and three years later when a staff meeting was held supposedly for nurses to address the issue it “had the effect of silencing the nurses’ concerns”.

Caroline Dinenage, the MP for Gosport, told the BBC: “It is utterly chilling. It’s almost heartbreaking. I don’t think any of us realised the scale of this. There are potentially over 450 lives shortened as a result of this. The report talks about a culture of shortening lives, it talks about a disregard for human life. It talks about families who thought their loved ones were there for respite and rehabilitation only to find that they were on a terminal care pathway. It is just almost unimaginable, this report and what it says.

“The government needs to look at this as a matter of extreme urgency. This is too big to ignore. This is over 450 lives shortened as a result of care.”