Sinn Féin President Mary Lou McDonald and Vice President Michelle O’Neill are set to meet with Scottish National Party leader John Swinney and Plaid Cymru leader Rhun ap Iorwerth in Cardiff on Monday to sign a joint memorandum advocating for national self-determination and referendums on constitutional change.

The meeting in Cardiff Bay brings together senior figures from the main pro-independence and nationalist political parties in Scotland, Wales, and Ireland. Organisers confirmed that the political leaders are participating in their capacities as party representatives rather than as official delegates of their respective devolved administrations.

The joint memorandum of understanding outlines proposed cooperation on economic policy, energy, European relations, and constitutional rights. The document sets out demands for democratic pathways allowing each nation to decide its future, including an Irish border poll governed by the provisions of the Good Friday Agreement, as well as mechanisms for Scottish and Welsh independence referendums.

The planned accord has drawn criticism from unionist politicians in Northern Ireland. Deputy First Minister Emma Little-Pengelly of the Democratic Unionist Party stated that O'Neill had not sought agreement or approval from her to attend the summit or sign any memorandum in her capacity as First Minister, emphasising that the initiative does not represent the shared Northern Ireland Executive.

The summit comes amid heightened political debate over constitutional jurisdiction, with UK Prime Minister Andy Burnham maintaining that holding independence referendums remains a reserved matter for Westminster and is currently off-limits.