The Stormont Executive has earmarked more than £57m this year to pay interest on its loans.
The money will meet interest payments on a variety of loans taken out over more than a decade.
However, despite repeated requests, the Department of Finance was unable to specify what exactly money has been borrowed and what for.
The projected interest payments of £57.5 million were outlined in a written answer from new finance and personnel minister Arlene Foster.
"The amount of interest payable in a given year depends on the level of outstanding loans in that year and the interest rate applicable to those loans," the minister said.
"The forecast interest payment in 2015-16 for borrowing under the Reinvestment and Reform Initiative (RRI) is £57.5m. This funding has been set aside in the executive’s budget 2015-16."
The RRI was set up in 2002 and was designed to enable Stormont to borrow up to £200m a year for infrastructure projects.
Interest rates are comparatively low and are set by the British Treasury.
To date, the executive has borrowed around £2bn and had hoped to draw down a further loan of £700m over several years for a large public sector redundancy scheme.
However, this has been jeopardised by the welfare reform impasse.
The RRI money has not been used solely for infrastructure projects and was, for example, used to fund the bail-out for Presbyterian Mutual Society investors.
SDLP assembly member Dominic Bradley described the interest payments as a "huge sum of money".
He said the executive needed to be cautious before agreeing to taking out more loans.
"These payments put a big hole in a shrinking budget and are a constant drain on our resources," he said.
"The executive should be clear what is and isn't a loan as they often give the impression new funds have been found when they are in fact being borrowed."
Mr Bradley added that he wanted to know the full extent of the executive's borrowings and was surprised DFP was unable to provide the Irish News with a comprehensive list.
