Almost £19m earmarked to help cut hospital waiting lists was spent on other things, the Health Minister has admitted.
Michelle O'Neill confirmed that only half of a £40m cash injection supposed to be used to ease the suffering of thousands of patients went on addressing the problem.
The remainder of the money, which was announced by former Health Minister Simon Hamilton in November last year, was used to address a range of other funding pressures, including independent care homes, domiciliary care providers and the GP out-of-hours service.
The matter came to light after UUP MP Tom Elliott wrote to Mrs O'Neill asking for clarification on how the additional money was used.
She explained that £21.5m was used to fund additional waiting list activity, while the remaining £18.5m was used on a range of other financial pressures during 2015/16.
In response, Mr Elliott branded the situation "shocking" and "abhorrent".
"One of the most regular complaints I receive from constituents concerns the absolutely appalling and inhumane lengths of time many are being expected to wait for medical treatment," he explained.
"When the Executive last year announced it had found an extra £40m of emergency funding to specifically tackle the spiralling waiting lists, it was understandably welcomed by many patients, who had been waiting months and sometimes years.
"Outrageously, however, 10 weeks after first asking how the money was used to benefit my constituents in the Western Trust, the minister informed me that only £21.5m of the original £40m earmarked for tackling waiting lists was actually spent on the problem."
Mrs O'Neill came under pressure yesterday to do more to tackle local waiting times during a debate on cancer services at Stormont.
A motion put forward by SDLP MLAs Colin McGrath and Mark Durkan, and UUP MLAs Jo-Anne Dobson and Robbie Butler, hit out at waiting times for cancer patients here.
It said that a crisis affecting cancer services was symptomatic of the "wider unprecedented crisis engulfing the Northern Ireland health service, with 392,000 people now on waiting lists". The motion additionally called on Mrs O'Neill to intervene to ensure patients received swift, safe and sustainable healthcare and to ensure patient safety was not further compromised.
Ms Dobson said: "My party warned... that the trusts were not given enough time to use this money on waiting lists.
"Time and time again, cancer waiting times have been raised in this house by successive ministers.
"When will these condemnations of the service they are leading be turned into actions?"
The failure to use the full £40m to help cut waiting times came to light just a number of weeks after the CEO of Northern Ireland's largest private healthcare provider claimed that pensioners were being forced to plunder their savings to pay for treatment.
Mark Regan said that elderly people were turning to their pension pots, savings and help from their children to pay for operations and procedures at private clinics because they are waiting so long to be seen by the national health service.
According to the most recent official figures, more than half of those waiting for inpatient or day case admission had waited longer than 13 weeks.
Almost one in 10 patients was waiting more than a year for inpatient treatment at the end of June.
This was a substantial increase of 13.9% compared to the end of March, and almost twice the number of people waiting at the end of June 2015.
In October last year, the chief executive of the Nuffield Trust health body said "heads would roll" in England if hospital waiting list figures were on the same scale as those seen in Northern Ireland.