SINN Féin has called for the establishment of a forum on Irish unity amid tensions between the DUP and foreign minister Simon Coveney, who has been criticised for "attacking" new British prime minister Boris Johnson.
Mary Lou McDonald was responding to warnings by Taoiseach Leo Varadkar that a no-deal Brexit would push moderate unionists and nationalists towards supporting unification.
She urged the Fianna Gael leader to "make it clear" that unity was the solution to the threat of a hard border, and called for the Dublin government to begin preparations ahead of any border poll.
"There is a momentum building for Irish unity and we need political, institutional and legislative arrangements in place to manage that," she said.
"That preparation must include the convening of an all-Ireland forum on Irish unity without delay. With the threat of a crash Brexit now a live prospect, it is irresponsible not to prepare for constitutional change."
Ms McDonald was criticised for the calls while telling new Secretary of State Julian Smith she hoped he would be the last British minister to hold the post.
Claiming her actions proved she did not care about "insulting unionists", Ulster Unionist MLA John Stewart accused Ms McDonald of being "detached from reality".
"Rather than engage in soundbites and rhetoric designed to persuade the Sinn Féin base that all is still on track, Sinn Féin would be better served by dropping red lines and getting Stormont back to work," he said.
Mr Johnson called yesterday for a renewal of "the ties that bind our United Kingdom" ahead of a trip to to Scotland to announce a £300m 'Growth Deals' funding pot for communities in the devolved regions.
"Our union is the most successful political and economic union in history. We are a global brand and together we are safer, stronger and more prosperous," he said.
"I'm proud to be in Scotland today to make clear that I am a passionate believer in our great union, and I look forward to visiting Wales and Northern Ireland to ensure that every decision I make as Prime Minister promotes and strengthens our union."
Under the latest Growth Deals plan, the funding will go towards deals in Falkirk, the Islands and Argyll and Bute in Scotland, Causeway Coast and Glens and Mid South West Northern Ireland, and Mid Wales.
Meanwhile, DUP MP Sammy Wilson has been told to "wise up" after demanding to known why Mr Coveney was given "permission" to make statements to the press at Stormont regarding Mr Johnson.
The Tánaiste told reporters that the prime minister's stance on a no-deal Brexit was "unhelpful" and placed the UK on a "collision course" with the European Union.
Insisting that Mr Johnson adhere to plans to leave the EU on October 31 with or without a deal, Mr Wilson said: "I will be enquiring as to who gave the Irish Foreign Minister access and permission to use Parliament Buildings for a press conference to attack the UK Prime Minister. If courtesies are going to be disrespected, then the matter will have to be carefully looked at."
SDLP leader Colum Eastwood told Mr Wilson to "wise up" in a tweet, while Alliance leader Naomi Long wrote: "Catch yourself on, Sammy. Seriously."
