Northern Ireland’s department of health “will welcome difficult questions” at a public inquiry into the alleged abuse of vulnerable patients at Muckamore Abbey Hospital, an inquiry has heard.

The Muckamore Abbey Hospital Inquiry is examining the allegations at the facility in Co Antrim.

The hospital, for adults with severe learning disabilities and mental health needs, has been at the centre of the UK’s largest ever police investigation into the alleged abuse of vulnerable adults.

A number of people are to be prosecuted in the probe.

Andrew McGuinness, counsel for the department of health, made an opening statement to the inquiry on Wednesday.

He said the department is confident the inquiry will be “comprehensive, searching and probing”, and it pledges to engage with it fully and transparently.

Mr McGuinness said the department would also like to publicly apologise again for the “appalling behaviours identified” and accept that practices “fell well short of what is acceptable”.

Outlining the changing structures of the health service in Northern Ireland over time, Mr McGuinness noted a “clear policy direction” from the 1990s that no-one should be required to live in long-stay institutions, and people with learning disabilities should be supported to live independently in a community setting.

He said there are 37 inpatients at Muckamore, reduced from 318 in 2005.

Mr McGuinness said allegations of abuse at Muckamore came to light in 2017 and further concerns were raised following viewing of CCTV footage.

He said the Belfast Trust commissioned an independent level three Serious Adverse Incident review of safeguarding arrangements, completed in 2018.

Later that year, senior departmental officials met with families of relatives affected, and an action plan was developed, with implementation monitored.

He also outlined a range of measures by Belfast Trust to ensure safe services at Muckamore, including CCTV in all wards, day care and swimming pool, viewing of footage selected at random and a significant reduction in the number of seclusion episodes as well as unannounced inspections.

Mr McGuinness described around 72,000 documents as potentially relevant to the inquiry, with 4,500 documents having been uploaded to the inquiry’s system.

“The department recognises the importance of the inquiry having all relevant documents and is engaging in a quality assurance process to ensure that no stone has been left unturned,” he said.

He added: “The department reiterates that it stands ready to co operate with and assist the inquiry in any way that it can, in particular given the important task of this inquiry, the department welcomes the difficult questions which are likely to come, and recognises that these will be essential to ensure fulsome answers and recommendations are produced by the inquiry.”

He said the department also wishes to repeat what was said by Health Minister Robin Swann when he announced the Muckamore inquiry, reiterating his apology as well as noting that families also deserve answers as to why this happened, and how it was allowed to happen.

“The department maintains this pledge to do all that it can to ensure this abuse never happens again,” he concluded.

Mark Robinson QC representing the PSNI, also made an opening statement on Wednesday.

Mr Robinson said they wish to acknowledge those at the heart of the proceedings, the patients and their families, commending their “dignity and fortitude”.

Referring to the ongoing criminal investigation, Mr Robinson said a “significant” police team continue to look at CCTV footage, triage incidents and interview suspects.

He described 300,000 hours, or 34.2 years of CCTV footage, which is likely to continue to be viewed until 2023.

Four files have been submitted to the Public Prosecution Service, involving 38 members of staff.

Mr Robinson said while the inquiry’s task is to look to accountability, the “only route to criminal accountability is through the criminal justice system”.

He urged all to “remain resolute in ensuring that there is no risk to that criminal justice process”.

“We must all jealously guard against any risk to that criminal justice process because if we don’t do that it may rob the patients, the families and the public of that individual criminal justice exercise,” he said.

The inquiry will resume on Thursday morning.