The Irish Financial Services Regulatory Authority has asked the boards of directors of 26 credit unions to examine whether they should take "remedial action" to deal with high levels of bad debt in their loan books.
The financial regulator has written to the boards in question, who have not been publicly identified, and told them to respond by the end of the summer.
The intervention follows the introduction last year of a quarterly reporting scheme under which credit unions must file regular returns to the financial regulator.
It comes only weeks after an internal report for the Irish League of Credit Unions warned that some of its members will probably go out of business because members were not repaying their loans.
That report also said a large number of credit unions were ignoring their bad debt issue or were not aware of their problem.
In an Irish Times interview, the financial regulator's chief executive, Pat Neary, said the figures provided by the 26 credit unions raised serious issues for them.
"They're serious enough for us to start to ask questions of the board at this stage. I don't want to raise any great sense of panic but in the sense that there would appear to be outliers from the averages, I think questions have to be asked and they have to ask the boards what actions they are going to take to bring their credit union back into line," he said.
"What we are saying to them is that the information you have sent to us suggests that your credit union figures are not as robust as the norm, that you are an outlier in some way".
"It could well be that you have indicated that you have a higher level of non-performing loans, however defined, and that the level of provisions that be may against those loans seems to be lower than the percentage of non-performing loans than the others, or that the number of loans in arrears as a percentage of your total loans seems to be higher than the others. That's at first look."
Mr Neary said the process was at an early stage only and that it could lead somewhere, or could lead nowhere.
"The next thing is you set out this information to the credit unions concerned and express our concerns that they are an outlier and ask the board of management to address this concern in the following way: review the figures; review the components of the figures; see if any remedial action is necessary; and give a timeline for putting the remedial action in place," he said.
