Three further suspects are to be questioned under caution in relation to the deaths of hundreds of patients at scandal-hit Gosport War Memorial Hospital.

An independent police investigation was launched into the community hospital in Hampshire after a probe found that hundreds of patients had their lives shortened through the use of opioids.

In 2018 the Gosport Independent Panel report concluded that the lives of more than 450 people had been shortened because of the routine practice of prescribing and administering opioids until the year 2000, and that probably at least another 200 patients were similarly affected.

The Kent and Essex Serious Crime Directorate, which is managing the investigation, codenamed Operation Magenta, has said it is reviewing the records of more than 750 patients.

The force previously said that 19 suspects had been identified to be interviewed for alleged health and safety offences but this number had now risen to 22.

Deputy Chief Constable Neil Jerome said: “The independent investigation into deaths at Gosport War Memorial Hospital is one of the largest and most complex of its nature in the history of UK policing.

“Our team consists of serving and retired detectives who have so far assessed more than three million pages of documents including the medical records of over 750 patients, and taken witness statements from more than 1,150 individual family members.

“The families of those who died at the hospital were informed at the start of the investigation that the full range of criminal offences would be considered, including homicide and any that may have been committed under the Health and Safety at Work Act.

“The families have since been updated that among the suspects identified by Operation Magenta are a number who are due to be interviewed under caution in relation to alleged health and safety offences.

“The investigation is ongoing and continues to make good progress.

“Whilst we have never provided anyone with an estimate of how long our inquiries will last, family members and the general public can be confident we are working as quickly and thoroughly as possible to ensure Operation Magenta is the decisive police investigation into what happened at Gosport.”

In June, the High Court agreed with the request by the families of Gladys Richards, Arthur Cunningham and Robert Wilson for new inquests to be held into their deaths.

Inquests were originally held into Ms Richards’s death in April 2013 and into Mr Cunningham and Mr Wilson’s deaths in March and April 2009.

The 2018 report said there was “a disregard for human life and a culture of shortening lives of a large number of patients” at the hospital.

It stated there was an “institutionalised regime of prescribing and administering ‘dangerous doses’ of a hazardous combination of medication not clinically indicated or justified”.

The inquiry, led by the former bishop of Liverpool James Jones, did not ascribe criminal or civil liability for the deaths.

The families say repeated ineffective investigations into hundreds of deaths at the hospital have left them without any justice or closure and have called for a new judge and jury inquest to be held rather than it be conducted by a coroner.