Taoiseach Leo Varadkar has said Ireland must be wise to the possibility of British prime minister Boris Johnson calling a snap general election in the autumn.
During a public interview at the MacGill summer school in Glenties, Donegal, Mr Varadkar also said that a hard Brexit would inevitably see communities in the North considering a United Ireland.
His remarks came as the sharp rhetoric between Dublin and London continues with Britain now looking on course to crash out of the EU without a deal.
Mr Varadkar and Mr Johnson have yet to talk by phone, more than two days after the British prime minister took up office.
Asked by Irish Times political editor Pat Leahy about Brexit and Mr Johnson's language in recent days, including demands to “abolish” the backstop in the Withdrawal Agreement, Mr Varadkar responded that this was politics.
He said that with the current parliamentary arithmetic that Mr Johnson was in a “weak position”. The new prime minister is also facing a threat from within the Conservative Party to block any no-deal Brexit.
Mr Varadkar said that nobody could discount the possibility that there could be an election in Britain before October 31.
But timing was everything, he said, and if Mr Johnson could deliver a deal on Brexit by October he would be in a different position. If he could not though and was blocked, Ireland needed “to be wise” to the chances of an election and a new House of Commons as early as September, he added.
There was, therefore, a need for the current confidence and supply agreement with Fianna Fáil to continue, he told the audience, and the deal with Fianna Fáil.
The Taoiseach said a no-deal Brexit would prompt more liberal unionists and nationalists in Northern Ireland to consider joining a united Ireland
He added that those uncomfortable with a “nationalistic” Britain which is considering reintroducing the death penalty could join forces to support Irish unity and continued membership of the EU.
However, he reiterated the Government is making no preparations for unity now, a key demand of Sinn Féin, since it believes that would be provocative to unionists.
The Taoiseach added Ireland’s negotiating aim for Brexit is to maintain the status quo on issues like cross-border trade.
The country is not using the issue to leverage constitutional change in Northern Ireland, he said.
“If there is a hard Brexit on the 31 of October, if the UK takes Northern Ireland out of the EU against the wishes of the majority of people of Northern Ireland and takes away their European citizenship and undermines the Good Friday Agreement in doing so, those conditions will arise whether we like it or not.”
Meanwhile, Sinn Féin leader Mary Lou McDonald has said there will be an interest in a border poll should there be a disorderly Brexit.
Speaking on Drivetime on RTÉ Radio 1, Ms McDonald said preparations for a border poll need to be carried out as a matter of urgency.
"This isn't about us looking to benefit or to profit from Brexit or to be mischievous," she said.
"In fact, we regard it as irresponsible for any...for each of the Government's to bury their heads in the sand at a time when we are facing potentially - in just over 90 days - perhaps a hard Brexit.
"That means that you have to consider and you have to prepare for all of the available options in terms of the border and removing the problems of the border."
Ms McDonald said the conversation on a united Ireland "is already underway".
She said that for a lot of people the issue of the border is now a matter "of membership of the European Union and people's sense of European identity."
Ms McDonald said her party want to have the debate on the border.
"If there is a disorderly Brexit there will be an absolute interest across the board, right across the island economically, socially and politically for the border poll to be held as soon as is possible."
She added that "the preparations need to start now."
"We need to afford our unionist colleagues and brothers and sisters the respect and the space to have their say in this debate, including for those for whom Irish unity wouldn't be their plan A or their first option.
"They too need to have a say and have a stake in terms of how we prepare for what I believe is now virtually an inevitability.
"I do believe that we're facing into a political scenario where there will be a border poll, where the question of constitutional change will be on the table."
Ms McDonald said she pressed Mr Smith on the issue of Irish unity, adding that she hoped he was the last British Secretary of State.
She said: “We have stepped through all of the issues with him and obviously the outstanding rights issues and the issues that need to be resolved to ensure that the institutions can be restored, and that, crucially, we can deliver inclusive, sustainable and good government for every citizen living in this part of Ireland.
“He is aware of the issues. He is aware that they have been well-rehearsed. He’s aware that this process of talks and negotiations has, to use his term, ebbed and flowed.
“He’s also aware that it needs to pick up momentum, that it can’t go on forever.
“He has committed that he will deal with all of the parties on the basis of equality and impartiality.”