Britain will vote on June 23rd in a referendum on its continued membership of the European Union. Two former British prime ministers, John Major and Tony Blair, warned on Thursday that if the Leave vote is successful, it would undermine peace in Northern Ireland and bolster the Scottish independence movement. They say this would jeopardise the unity of the United Kingdom.

"It would be a historic mistake to do anything that had any risk in destabilizing the complicated and multi-layered constitutional settlement that underpins the current stability in Northern Ireland, but that is what a British exit from the European Union would do," Major said.

"Here we stand as two former Prime Ministers and we say to the Leave campaign very directly: you have fundamental questions to answer about Northern Ireland, about the common travel area, about the effect of leaving the EU, on the future make up of the United Kingdom," Blair said.