Fianna Fáil leader Micheál Martin has said that the Taoiseach made a mistake with his comment that he “could not deliver unionism”.
“While it's not his entire function to deliver unionism, I think we have to work with unionism because I think to be fair Reg Empey and people have come forward with interesting ideas in the last month around the problem and situation.
“We all have to live on the one island, we have to continue to do that in harmony and I think we need to work together to make sure we do that,” Mr Martin told RTÉ radio’s Morning Ireland.
Unionists understand that a no-deal Brexit will be very bad for Northern Ireland, he said.
“We need to ensure and give guarantees that whatever materialises, whatever northern specific arrangements could emerge would not undermine the constitutional status of Northern Ireland as per the Good Friday Agreement.
“There may be a necessity for an enhanced form of consent around all of this at the end of the day.”
Mr Martin also said there would be no “red lines” for Fianna Fáil in budget negotiations under the Confidence and Supply Agreement.
His party wants greater emphasis on services such as health and housing.
This year there will be further emphasis on older people to ensure they have the resources to access services, he added.
He also said he is in favour of the introduction of a carbon tax which could be “€5 or €6” within a 10-year framework.
However, all funds raised through the carbon tax should be ring-fenced for climate change projects.
Mr Martin said he did not anticipate a general election before Spring 2020, but that it was up to the Taoiseach to decide when the next election will be held. “We won’t pull the plug.”
The “basic issue”, he said is “we need to see clear light at the end of the Brexit tunnel.”
He said that his own preference is to lead his party in a Government with a number of smaller parties. “The old system is gone.”