Fianna Fail leader Micheal Martin has said the Government should look closely at a Northern Ireland-only backstop.
Speaking at his party's annual Parliamentary Party meeting in Gorey, Co Wexford, on Monday, Mr Martin said he felt the idea of a Northern Ireland-only special economic zone was favourable.
"A Northern Ireland-only backstop, I think, is still on the table," he said.
"We have always felt there should've been a special economic zone for Northern Ireland, adamant that it would not undermine the institutions underpinned in the Good Friday Agreement.
"Unionism seemed to very early on turn against the idea.
"If enough guarantees can be given there to ensure the constitutional framework of the Good Friday Agreement prevails, in the context of a Northern Ireland-specific arrangement, there may be potential for an exit agreement to be arrived at.
"I think we all have to be open to that possibility.
"Deep down, I feel unionism knows that no-deal will be ruinous for Northern Ireland."
Fianna Fail currently props up the Government's Fine Gael party in a confidence and supply arrangement, which it has previously said it will not disrupt until after Brexit for the sake of the country's political stability.
A general election is widely expected sometime in the new year.
The prospect of a Northern Ireland-only arrangement has been re-suggested after the Irish Premier conceded that checks will be required close to or around the Irish border in the event of a no-deal Brexit.
"I don't think the Government were telling us the truth when they said there would be no checks in no-deal," Mr Martin added.
"That position has changed and now they've said there will be checks somewhere, a completely different position than that which was articulated last January.
"The issue of course is, in a no-deal, Britain becomes a third country and the EU wants its border protected."
Asked about Boris Johnson's visit to Dublin on Monday, Mr Martin said he was heartened by the Prime Minister's declaration that he wanted a deal.
"I welcome Boris Johnson's comments that he wants a deal; equally, Amber Rudd said in the brief time she spent in Cabinet that she got the sense that all the effort was towards a no-deal," he said.
"It is worrying when someone like Amber Rudd says there is little focus on preventing no-deal; the one hopeful situation is that Boris Johnson is in a tight corner now.
"Parliament has constrained him significantly, and he also has a situation within his own party - there are those who will not tolerate a no-deal.
"He is a political operator primarily but there may be other options to avoid a no-deal."
The Fianna Fail leader also said the Irish Government is more interested in "spin" than substance.
"The defining characteristic of this Government is spin rather rather than substance of what they should be about, which is giving people the detail around a no-deal Brexit, telling us the truth about what will happen at the border and how the talks at the EU Commission are going.
"It's silly stuff and I'm not too exercised by it; when people start attacking you sometimes it can be a compliment."
