Northern Ireland's ruling parties will adopt a "joined-up" approach to dealing with Brexit, despite their opposing stances in the referendum, Martin McGuinness has insisted.
The Sinn Fein Deputy First Minister said his party and the Democratic Unionists had held a "number of conversations" and had resolved to work together to secure the best outcome for the region in the EU exit negotiations.
His comments came as DUP First Minister Arlene Foster faced down claims she had performed a U-turn over her support for Brexit.
Political rivals levelled the accusation against Mrs Foster after she and Mr McGuinness, a Remain advocate, jointly penned a letter to Prime Minister Theresa May outlining a series of risks presented by leaving the EU.
The content and tone of the letter have been characterised by some as pro-Remain.
While the UK as a whole voted to leave the EU in June's historic referendum, in Northern Ireland 56% backed Remain.
Mr McGuinness dismissed the criticism of Mrs Foster as "political point scoring".
"It's very important, given we were on different sides of the debate in the run in to the referendum to, in the aftermath of the vote, to come together to do the best we can to protect the interests of the people we represent," he said.
"Both of us could have put our heads in the sand. We are not prepared to do that. We have been charged by the people to jointly lead this administration and that's exactly what we are going to do."
The republican veteran said Mrs May had indicated during last month's meetings at Stormont Castle that she would trigger Article 50 of the Lisbon Treaty - to commence the Brexit negotiations - "in the early part of next year".
"So we have to deal with that," he said.
"We can't ignore the political realities that are ahead of us and we have to do the best we can to ensure that as an administration we are as joined up as we can be."
He added: "People are looking for a division or a points scoring exercise by me over the DUP, well that would be irresponsible leadership in my opinion.
"This is too big, this is too serious for our economy, for our future, for us not to be joined up in relation to how we take this process forward.
"So I intend to be very joined up against the backdrop of the history of where we have come from, and the fact there was a vote, a vote we were on different sides of.
"The vote is over - now we have to deal with the reality and the challenges that that poses to our community."
Mrs Foster has faced questions over her Brexit position after the publication of the letter she and Mr McGuinness sent to Mrs May.
It highlighted a number of issues that could negatively impact on Northern Ireland.
Mrs Foster rejected the suggestion she had had a change of heart.
"Brexit means Brexit and our Prime Minister is very clear about that and I support her in that," she said.
"That doesn't mean to say we close our eyes to some of the immediate challenges that are there.
"We have set out those challenges and now we move forward in a positive way."
Of the five main parties in Northern Ireland, Sinn Fein, the SDLP, the Ulster Unionists and the Alliance Party all campaigned for Remain while the DUP, the region's largest party, backed Brexit.
Mrs Foster and Mr McGuinness's joint letter to Mrs May stressed that Brexit could not be allowed to compromise cross-border efforts to tackle organised crime and those opposed to the peace process.
The ministers also said it was critical to the economy that businesses retained their competitiveness and did not incur additional costs. It highlighted the need to retain access to sources of skilled and unskilled labour in the EU.
The vulnerability of an agri-food sector reliant on EU subsidies was also raised, as were concerns that a proportion of billions of euro of EU funds for projects in Northern Ireland may not be drawn down due to the exit.
Mrs Foster said Brexit would open up great opportunities for Northern Ireland but that it was right for her to highlight issues of concern.
She told BBC Radio Ulster: "It would be negligent of me not to point out where I believe the challenges are, because we are going into the all-important negotiation with our national government (with the EU)."
She added: "We are extracting ourselves from the European Union and it is right we identify where those challenges lie, but I fundamentally believe there are huge opportunities."
Ulster Unionist economy spokesman Steve Aiken said: "Given the content of the letter, I would question whether this is a DUP U-turn on their position on the referendum after the vote has taken place."
Jim Allister, leader of the Eurosceptic Traditional Unionist Voice party, said: "This letter illustrates an overriding desire by the DUP to pander to the Sinn Fein position of seeking to row back on the decision of our nation to leave the EU.
"The tone and content of this letter is so strongly pro-EU that it is hard to imagine it is co-authored by a party that campaigned for Brexit."