In a strongly-worded statement Sinn Fein has called for a referendum on a united Ireland after accusing English voters of "dragging Northern Ireland out of the EU".
In Northern Ireland 440,707 (56%) people voted to Remain and 349,442 (44%) voted to Leave.
Of the region's 18 constituencies, 11 voted Remain and seven voted Leave.
Sinn Fein's national chairman Declan Kearney said the question of Northern Ireland remaining as part of the UK had now been brought into sharp focus.
English votes have overturned the democratic will of Northern Ireland. This was a cross community vote in favour of remaining in the EU.
English voters are dragging Northern Ireland out of the EU.
This British Government has forfeited any mandate to represent the economic or political interests of people in Northern Ireland
Mr Kearney added: "We now have a situation where Brexit has become a further cost of partition, a further cost of the Union and Sinn Fein will now press our demand, our long standing demand, for a border poll."
But the Democratic Unionist Party's Sammy Wilson warmly welcomed the likely Brexit.
He said: "The future for Northern Ireland will be as bright as the future of the United Kingdom is going to be."
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