There have been calls for "transformational reform" of the health system after it emerged that the amount spent by health trusts on locum doctors has increased by 43% since 2016 - with last year's bill coming to almost £100m.
In response to growing pressures facing the health system, the cost of employing these doctors has been on the rise for years.
Trusts employ locum staff for several reasons, such as to cover for sickness and maternity leave, to cover for existing vacancies, and when demand increases in the winter months.
In the 2020/21 financial year, a total of £98.6m was spent on agency doctors, with the Western Trust having the highest expenditure in this area at £24.5m, following by the Belfast Trust at £22.8m.
Over the 2016/17 financial year, the total bill was £68.6m. In the last five years, £422.8m has been spent on locum doctors.
SDLP health spokesperson Cara Hunter said that the region's over-reliance on locum doctors is nothing new, but despite the small increase on last year "people will be shocked to learn this year’s bill runs to nearly £100m".
"This is completely unsustainable and cannot continue. Given the financial pressures across our health service as it lurches from one crisis to the next much of this £100m could have gone to better use elsewhere.
"We need to seriously and strategically address workforce planning issues. All of the evidence tells us that new graduates are likely to take up offers of employment close to where they studied. That’s why the SDLP has made the case for the medical school at Magee to create a solid supply of medical graduates who can help to address vacancies and workforce planning issues.
"Our health service simply cannot afford to pay these huge sums to locums every year and it’s beyond time that we applied a strategic approach to the problem.”
"Coupled with this has been poor workforce planning and a slow pace as regards the transformational reform. Therefore, it is hardly surprising this cost is so high," she said.
“It is imperative, however, new systems are put in place to mitigate against these costs and ensure scarce public finances are used optimally.”
The Department of Health (DoH) said the primary aim of using locum staff is to ensure that safe and effective services are sustained at all times for patients and clients.
"The Department is committed to sustained investment in growing the local workforce to meet ever increasing demands, for example, this year we have maintained pre-registration nursing and midwifery training places at the record high level, (1,325)," it added.
"Furthermore, the first cohort of 70 students for the Northern Ireland Graduate Entry Medical School is due to commence in September this year.
"In addition, a Regional Agency Reduction Implementation and Planning Group has been established to co-ordinate the improvement of staff utilisation, with the aim of reducing unsustainable agency spend, beginning with off-contract arrangements.
"The main function of the group is to develop and implement a plan, with local and regional commitment and coordination, to safely facilitate, and manage the service impact of, reducing unsustainable agency and locum spend."