NEW: Plaid Cymru, SNP and Sinn Féin have signed a memorandum pledging closer cooperation and arguing that Scotland, Wales and Ireland have the right to determine their own future.

NEW: Plaid Cymru, SNP and Sinn Féin have signed a memorandum pledging closer cooperation and arguing that Scotland, Wales and Ireland have the right to determine their own future.

The parties say that "Westminster's time is coming to an end" and that the constitutional change is gaining momentum.

They say the future of their countries belongs to the EU and insist that no Westminster government has the right to block self-determination.