Sinn Fein's National Chairperson Declan Kearney has warned that there is a risk that the peace process could be "squandered" by Brexit coming on top of the collapse of political institutions in the North.
Kearney said the "catastrophe of Brexit" had been "torpedoed" into a society already struggling with the failure to fully implement and defend the 1998 Good Friday Agreement.
"There is a need for us all to look beyond the existing crises and challenges and to provide hope and positive vision," he said. He argued that a new generation is now "questioning partition and its abject failure".
"Partition is the central fault line at the heart of Irish politics and society. It has been an abject failure from its imposition," he said. "The greater majority of citizens in the north are committed to the Good Friday Agreement. They want rights to be guaranteed which are already enjoyed by others in Dublin, London, Edinburgh and Cardiff. They seek a rights based society copper fastened by the Bill of Rights enshrined within the Good Friday Agreement."
Concern is mounting that the Six Counties are set to be taken abruptly out of the EU against the will of the people in both parts of Ireland. In that case, the rights safeguarded by the Good Friday Agreement under the EU Charter of Fundamental Rights and the European Court of Justice will be lost. Online opinion polls have claimed that increasing numbers of people in the North are now in favour of reunification.
Mr Kearney said the "political earthquake" of Brexit had again exposed the negative role that partition plays in Irish affairs, and the fundamentally anti-democratic nature of the union of the North with Britain.
"Brexit has become a defining moment for these islands. The debate on Irish unity and the timing of a unity referendum have now moved centre stage," he said.
"Negative mismanagement of the Irish peace process and the Good Friday Agreement by successive British governments, and the particular pro-unionist bias of the Conservative government since 2010, must be replaced with a recognition that the transition towards Irish unity should begin.
"Brexit means that change in the political relations between Britain and Ireland is now unavoidable.
"In parallel, the Irish government needs to begin to prepare for the constitutional, political and economic transition towards Irish unity.
"The Irish government should commence a discussion with the EU Commission and institutions to explore their practical role and support in facilitating an efficient process of reunification."
