The SDLP and Fianna Fáil have issued a joint statement urging pro-remain parties across Ireland to form an alliance.
The statement, which was issued by party leaders Colum Eastwood and Micheál Martin, sets out five core principles for parties across the island to agree on, in order to counteract the consequences of Brexit.
The release is one of the first statements sent from the parties on a joint basis since they announced their partnership in late January.
"It is just 36 days until Brexit and with each passing day the UK edges ever closer to crashing out of the European Union without a deal," the statement reads.
"The arithmetic in Westminster no longer allows us to leave anything to chance.
"Brexit can only be stopped by actions, not words or placards. Extraordinary times call for more than ordinary measures.
"Together, pro-remain parties must agree and act upon a set of principles that ensure the protection of people across this island, from Derry to Cork.
"Together, the SDLP and Fianna Fáil agree that all pro-remain parties must recognise and invoke five core principles necessary to stave off the worst outcomes of Brexit."
The statement continued with the following list of principles:
1. "The key to forming a pro-remain alliance worthy of more than joint press statements lies in the restoration of Stormont. An Executive is vital if we are truly to protect our economy, farms and businesses from the fall-out of Brexit."
2. "We must stand firm on the backstop."
3. "It is simply not enough to oppose a no-deal Brexit - it must be voted down. All pro-remain parties have a duty, whether it be in the Assembly, the Dáil or in Westminster to make every vote count."
4. "We must recognise that both unionists and nationalists voted to remain. And of course, the impacts of Brexit will adversely impact everyone regardless of political affiliation. Therefore, pro-remain parties must commit to reassuring unionists that constitutional change can only come about through the mechanisms outlined in the Good Friday Agreement."
5. "Pro-remain parties must recommit to reconciliation. We must work to ensure that peace, through the spirit that delivered the Good Friday Agreement, is a priority we never let slip."
Talks about a possible merger between the two parties had been ongoing for a number of months prior to the announcement, however the current partnership is on the basis of a programme of public engagement and common policy proposals on economic development, Irish unity, Brexit, education, health, and housing.
The fallout of the decision had an impact on the SDLP, which saw a number of figures resign from leadership positions within the party.
The chairpersons of the SDLP Youth, Women and LGBT+ branches quit the roles, as well as south Belfast MLA Claire Hanna, who left her role as the party's Brexit spokeswoman, and resigned from the party whip.
Ms Hanna wrote on social media: "I remain unconvinced that an exclusive partnership with Fianna Fáil is the right vehicle with which to deliver the non-sectarian, transparent and social democratic new Ireland I believe in."