THERE have been more than 2,000 'serious adverse incidents' (SAIs) in hospitals across the north in the past five years.
More than 1,800 legal cases have also been taken against health trusts since 2011, with £120 million paid out as a result.
SAIs are defined as events which "have or did lead to harm, loss or damage to people, property, environment or reputation", and include unexpected/unexplained patient deaths.
The number has been rising since 2011, when 242 such cases were recorded.
That increased to 383 by 2013, before almost doubling to 730 the following year.
There was a slight reduction last year, with the total dropping to 604.
SAIs are broken down by health trust rather than hospital and show the Belfast area saw the most incidents - 583 over five years - followed by the Northern Trust at 531.
The Irish News reported last year that around 83,000 "adverse" incidents are notified to authorities each year but only one per cent of these are classed as Serious Adverse Incidents.
The figures were released by health minister Michelle O'Neill in response to a written assembly question from UUP Lagan Valley MLA Robbie Butler.
Mr Butler said: "Whilst the vast majority of local patients do receive a good service, primarily thanks to the sheer dedication and grit of our health service staff, the 150% increase in the numbers of Serious Adverse Incidents between 2011 and 2015 is deeply concerning.
"Whilst I am aware that the categorisation of SAIs has widened slightly over recent years, this simply cannot account for the upsurge in the numbers of incidents being reported.
"The increase therefore has been caused by other reasons and I am fearful that the growing staff and resource pressures currently engulfing our local hospitals may have been a contributory factor."
An Audit Office report last year pointed to a "blame culture" that prevents frontline staff from reporting errors.
"Changing the culture within the health and social care sector from one of fear to an eagerness to report, explain and learn from what went wrong will only happen through cultural change," Comptroller and Auditor General Kieran Donnelly said.
Last month Belfast Coroner's Court heard how the Northern Trust produced an SAI report about the case of Glengormley woman Edel Houston (23), who died in June 2015 at Antrim Area Hospital after suffering a seizure and cardiac arrest following an overdose of caffeine pills.
The court was told that she was not attended to by triage staff until 45 minutes after her arrival at hospital.
