The Irish Congress of Trade Unions has called on its members to vote Yes in the Lisbon Treaty referendum.
The Executive Council of the ICTU has voted by a majority of 14 to 5 in favour of supporting the Treaty.
Unite and the TEEU voted against supporting it, whilst SIPTU and Mandate abstained from voting at all.
SIPTU, which represents about a third of ICTU's membership, will decide on its position next week.
However ICTU General Secretary David Begg has said it remains to be seen if the 600,000 strong membership takes heed of the advice of Congress.