The chairwoman of an inquiry into more than 2,000 mental health-related deaths has said “we may never know” the true number of people who died.

The Lampard Inquiry has got under way, examining deaths at NHS-run children and adult inpatient units in Essex between 2000 and 2023.

Baroness Lampard, who is leading proceedings, said the inquiry was “of the gravest concern and significance”.

She warned the number of deaths was expected to be “significantly in excess” of the 2,000 figure previously reported.

Families unfurled banners and laid posters and placards on the floor outside the Civic Centre in Chelmsford ahead of the first session.

“The tragedy is that we may never have a definitive number of deaths,” Baroness Lampard said in her opening remarks, adding the scale was “deeply shocking”.

“We may never be able to say for sure how many people died,” she said.

Baroness Lampard also paid tribute to the “dedicated and tireless campaigning” of bereaved families.

The inquiry was fixed to focus on Essex Partnership University NHS Foundation Trust (EPUT), the North East London Foundation Trust (NELFT) and organisations that existed previously.

It will not be looking at deaths in the community unless they happened within three months of discharge from a mental health unit, the patient had been assessed and refused a bed or they were on a waiting list for a bed.

The first week of the inquiry is hearing opening statements from Baroness Lampard and legal representatives, before bereaved families read statements from next Monday.

The full report from the inquiry could take “a few years” before it will be published.

Baroness Lampard said it would be “fair, objective, rigorous and balanced”.

EPUT chief executive Paul Scott said his thoughts were with those who had lost loved ones.

However, he disputed the 2,000 deaths figure made public by the inquiry.

He said it included deaths from natural causes, for example where some patients may have been transferred to hospital after a heart attack.

“Patient safety is our absolute priority and we are committed to learning from the work of the inquiry,” Mr Scott said.