At least 200 more people were "probably" similarly affected.
"They show too that, whereas a large number of patients and their relatives understood that their admission to the hospital was for either rehabilitation or respite care, they were, in effect, put on a terminal care pathway".
Patients and relatives were marginalised by the professional staff.
It added: "The families, and indeed the nation as a whole, are entitled to ask how these events could have happened; how the hospital dismissed the nurses' concerns and subsequently took no action; how the healthcare organisations failed to intervene".
The Gosport Independent Panel will present the findings of its £13 million investigation, first launched in 2014.
Many of the Gosport campaigners are now demanding criminal charges be filed against those responsible. The families gathered near Portsmouth Cathedral after the report was released, clutching photographs of the dead and holding them up for the cameras.
Among them was Bridget Reeves, the granddaughter of one of the victims, Elsie Divine.
She said: "I think there is somebody that needs to be prosecuted for what's gone on there".
"They have grossly failed their ethical standards by abusing people's human rights", she said, recalling "vulnerable relatives who were stripped of their final words to their loved ones, silenced by overdoses".
"That remains the case but it is already apparent from our early reading of the 370 pages that in its deliberations, the Panel has had sight of information that has not previously been seen by Hampshire Constabulary".
Eric Cousins, 71, son of war veteran Arthur Cousins, who also died aged 82 in the hospital, said: "I'm afraid we do need people's heads for it".
The inquiry into what happened at Gosport War Memorial Hospital is being led by the former bishop of Liverpool, the Rt Rev James Jones.
Dr Jane Barton, a local GP who cared for the some of the patients at Gosport, was found guilty in 2010 by the General Medical Council of "serious professional misconduct" after it concluded that she had prescribed potentially hazardous levels of drugs.
In an interview with BBC Newsnight Norman Lamb spoke of his anger when department of health officials advised him in 2013 that a public enquiry should not be held after the publication of an official report into the deaths.
Bishop Jones chaired the Hillsborough Independent Panel whose work in examining documents and evidence led to the new inquests into the deaths at the 1989 disaster.
The panel found there was "no medical justification" for such strong painkillers being used.
The report noted the Gosport deaths and the concerns raised about them occurred at the same time as it was revealed that British family physician Harold Shipman, dubbed "Dr Death" had been responsible for killing patients in his care with lethal heroin injections.
The panel also highlighted shortcomings from surrounding services around Dr Barton during the 1990s: citing hospital management, Hampshire Police, the Crown Prosecution Service (CPS), General Medical Council (GMC), and Nursing and Midwifery Council (NMC), "all failed to act in ways that would have better protected patients and relatives", the panel said.