Junior Defence Minister Paul Kehoe has refused to rule out using a veto to prevent the association representing enlisted personnel, PDForra, from becoming affiliated to ICTU.
The umbrella union group has signalled that it is prepared in principle to bring PDForra under its wing so it can be represented at national pay talks.
Mr Kehoe said he is awaiting a report from his department officials which will take in the opinions of all concerned, which will also include the views of Chief of Staff Vice Admiral Mark Mellett, and RACO which represents officers in the Defence Forces.
He did not say when he was likely to receive the report or if he would make a decision on the matter before addressing PDForra's annual conference which is due to take place in Co Carlow next week.
The chief of staff told the RACO conference that the Department of Defence has previously indicated that the right to affiliate or associate with ICTU poses complex questions for the Defence Forces from a legal, operational and management perspective.
“A key concern, expressed by Minister Kehoe, is that such an affiliation would carry obligations that would be incompatible with military operations and the roles assigned to the Defence Forces,” Vice Admiral Mellett said.
“I have been consistent in always saying that the military must be subservient to the political. In a healthy democracy, there can be no other way. Óglaigh na hÉireann is a key component of the security architecture of the State.
“Clearly, the taking of any form of industrial action is incompatible with military service. Any diminution of the institutional arrangements that guarantee the unconditional availability of the services of the Defence Forces for Government has potential implications for State security,” he said.
“RACO has made no secret of the fact that we have reservations about the application for affiliation to ICTU of our sister association.
“We have continually held that an independent pay review body is the preferred solution in our view,” RACO president Comdt Shane Keogh said.
His counterpart in PDForra, Mark Keane, said his 6,500 members have no intention of ever engaging in any form of industrial action. He said the only reason they sought ICTU affiliation was so they could be represented at the next round of national pay talks.