Fianna Fáil and Northern Ireland's SDLP have issued a joint statement, urging pro-remain parties across Ireland to form an alliance to help offset any fallout from Brexit.
It sets out five core principles, including standing firm on the border backstop and voting down any no-deal options.
"The arithmetic in Westminster no longer allows us to leave anything to chance", the statement said.
"Brexit can only be stopped by actions, not words or placards."
"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."
It also called for recognition that both unionists and nationalists voted to remain.
SDLP leader Colum Eastwood says 'extraordinary times call for more than ordinary measures'.
"I think it's very clear that we're in a very difficult time and actually a national emergency.
"We have lots of people saying they're opposing Brexit, and they want to support the backstop and they want to stop us having a hard border - but what we really need is action.
"We need Stormont to be brought back, we need the backstop supported, we need people to turn up in Westminster to vote against a very hard Brexit".