Britain should commit to holding a vote to unite Ireland if its citizens choose to leave the European Union in a referendum in June, Northern Ireland's nationalist deputy first minister said on Friday.
A so-called "Brexit" would represent a "political and economic game changer" for the island of Ireland, Martin McGuinness of the Sinn Fein party said, calling for an immediate border poll if Britain voted to leave.
Sinn Fein, which is predominantly supported by Catholic Nationalists who remained part of the United Kingdom in a province dominated by Protestants after the Irish state secured independence from Britain in 1921, is campaigning for Britain to remain inside the EU.
"If Britain votes to leave the European Union then that could have huge implications for the entire island of Ireland and, given all the predictions, would run counter to the democratic wishes of the Irish people," McGuinness said in a statement.
"If there is a vote in Britain to leave the EU there is a democratic imperative to provide Irish citizens with the right to vote in a Border Poll to end partition and retain a role in the EU."
Although pro-British Protestants still make up a majority of the Northern Irish population, Sinn Fein has been gradually increasing a push for a border poll which is allowed no more than once every seven years under the 1998 Good Friday Agreement peace deal.
Britain's Secretary of State to Northern Ireland may call a border poll at any time, according to the 1998 agreement that brought about peace. It also specifies that the Secretary "shall" order a referendum if it appears likely that a majority of those voting would seek to form part of a united Ireland.
A BBC/RTE survey in November found that just 30 percent of voters in Northern Ireland would like to see a united Ireland in their lifetime.
Many in Northern Ireland fear that new border restrictions resulting from a "Brexit" could re-energise nationalist demands for a unification which helped fuel three decades of violence with the British authorities and unionists who want to remain part of Britain. At least 3,600 people were killed in the "The Troubles".
Northern Ireland's Democratic Unionist Party, the province's largest party that shares power with Sinn Fein, is campaigning for Britain to leave the EU.