More than £125m has been paid to private healthcare operators to tackle shortfalls in Northern Ireland's health service.
The expenditure, over a five-year period, was used to address pressures and waiting lists, for example outsourcing procedures to private health providers.
The figure emerged as the Health Minister said the sector would require extra funding of £661m next year.
Robin Swann said there were "deep-seated problems across the health and social care system that will take years to put right".
Official figures revealed how the Department of Health has turned to the private sector.
Such firms are used so patients can be seen sooner and to help health trusts meet targets.
In the five years to April last year, the cost topped £125,540,000 - equivalent to £70,000 a day on average.
The figures were disclosed by Mr Swann after an Assembly question from Jim Allister.
Mr Swann said: "The HSC utilises the private healthcare sector where in-house capacity is unable to meet demand."
However, TUV leader Mr Allister said the spending should be properly scrutinised.
"Taken in totality, the level of expenditure is very considerable," he said.
"That is money that should be spent in the public sector, not the private sector.
"The fact it is going to the private sector shows that there has been too little focus and attention on building up a public health system."
A breakdown of spending showed £41.16m was paid to private companies in 2014/15, with a further £35.15m in 2015/16. Expenditure fell to £23.53m in 2016/17 and £8.29m in 2017/18. However, in the last year (2018/19), spending started to rise again and reached £17.41m.
Official figures show Northern Ireland's waiting lists are continuing to grow.
The latest statistics showed the number of people waiting more than 12 hours in emergency departments had more than doubled in a year - up from 1,991 in December 2018 to 5,280 in December 2019.
Last week this newspaper revealed a patient waited 60 hours in the casualty unit at Antrim Area Hospital in December.
Dr Tom Black, chair of the British Medical Association's Northern Ireland Council, said expenditure on the private health sector was further evidence of the need to transform the health service. "These figures are no surprise and are a side effect of years of poor workforce planning and chronic under-investment in the health and social care service," he added.
"Poor workforce planning leads to over-use of locums, decline in service delivery, stress on existing workforce and long waiting lists - waiting list times that are currently the worst in the UK and growing.
"The use of private providers to tackle waiting lists is a costly fix to a problem that can only be properly addressed through full-scale transformation, as outlined by Professor Bengoa. That includes implementing the workforce planning strategy and ensuring it is resourced effectively and takes in primary, secondary, community and social care."
The Department of Health said: "Where health service capacity is insufficient to meet demand for elective services, trusts have been funded non-recurrently to undertake additional activity to further increase the number of patients receiving assessment or treatment.
"Trusts are expected to maximise in-house capacity in the first instance. However, a proportion of patients will be transferred to private healthcare providers when insufficient capacity is available within the HSC.
"The HSC has arrangements in place to ensure that the sourcing and procurement of additional capacity is managed efficiently and effectively."
On Tuesday Mr Swann said an extra £492m would be required compared with this year's budget just to maintain existing service levels. Meeting commitments on restoring pay parity and improving staffing levels will require another £170m.
He said the 2020/21 budget his department receives next month would be crucial.
Mr Swann accepted he was requesting a significant amount of additional money.
"I very much welcome the priority attached to health by Executive colleagues both in public and in private. We are all facing up to the scale of the challenges in our departments," he said.
"I certainly owe it to patients and their families to be frank with them."