Martin McGuinness has accused the Government of being on a collision course with the EU over Brexit.
The Deputy First Minister warned that Northern Ireland would be "collateral damage".
He was speaking after Prime Minister Theresa May said on Sunday that she would trigger Article 50 by the end of March.
Mr McGuinness claimed Northern Ireland would suffer economically and politically.
"It is quite obvious the British Government is on a collision course with the EU in which our economy and successive agreements are regarded as collateral damage," he said.
"This is more about the internal division within the British Tory party, which clearly has no clue whatsoever about what it is facing.
"The Tories clearly do not care about the people of the North who clearly voted to remain in the EU. None of this is a done deal and it is important that people mobilise in a campaign to confront the selfish approach of the British Government which holds out the potential to hugely damage our economy.
"There is also a need for the Irish Government to act on an all-Ireland and European level to represent the democratic wishes of the people of the North and respect the remain vote."
Meanwhile, an SDLP MP on the Westminster committee examining Northern Ireland's post-Brexit border believes a return to the control policies in place during the Troubles is entirely possible.
The lone nationalist voice on the committee, former SDLP leader Alasdair McDonnell, said he wants to see the open border being maintained.
However, he believes that the return of strict checks at ports and airports, along with some type of land checkpoint, is the most likely outcome.
He sits on the House of Commons Northern Ireland Affairs Committee which is looking at the future of the border.
"We're probably going to go back to the arrangement that we had for the movement of people during the Troubles where basically Heathrow Airport and Holyhead and places like that were points of maximum scrutiny," he said.
"I would hope there'll be relatively free movement of people across Ireland."
Ulster Unionist Danny Kinahan MP said a physical border will have to be in place until new agreements on the movement are reached.