The Social Democratic and Labour Party (SDLP) has voted 'decisively' in favour of a partnership with Fianna Fáil.
At a conference this afternoon in County Down, roughly 70% of members backed the move, with 30% against.
SDLP leader Colum Eastwood said it was a momentous day for the party:
"We had a very good robust discussion and we decided with a huge majority to support the leadership proposal to go into a policy partnership with Fianna Fáil.
"The vote was decisive, it was 70/30 and what we have to do now is unite behind that result and work together and deliver for the people that we need to deliver for."
The Labour party said in a statement that it was dissappointed by the result of the vote:
"It remains our view that this move represents a precursor to a full merger. We also note that 30% of delegates opposed the leadership motion.
"The consequences of the partnership decision will now be carefully considered by the Labour Party in the coming weeks, and in consultation with our colleagues in the Party of European Socialists.
"The Labour Party remains committed to supporting those who wish to maintain Labour politics and the social democratic tradition in Northern Ireland."