The Comptroller and Auditor General says religious congregations have so far handed over just 13% of the cost of the child abuse redress scheme.
The congregations are supposed to pay the costs with the State on a 50-50 basis.
A special report has also found that legal cost payments of almost €200 million have been paid, with some legal firms getting between €5 million and €19 million.
The initial child abuse inquiry was estimated to cost €2.5 million, but the report says the cost of the commission is now €82 million.
Seamus McCarthy’s report also says the redress scheme was estimated to cost around €250 million – the bill to the end of 2015 is five times that.
The total costs of over €1.5 billion were to be split 50-50 between the State and Religious congregations, meaning the church would have to contribute €760 million.
This report finds the congregations have so far offered the equivalent of about 23% of the cost, while contributions actually received represent about 13%.
Legal cost payments of almost €193 million have been paid to 991 firms – 24 of those have received at least €1 million.