Leaders of nationalist parties in Wales, Scotland, and Northern Ireland signed a memorandum of understanding in Cardiff on Monday, calling on the UK government to prepare for constitutional change.

Plaid Cymru leader Rhun ap Iorwerth, Scottish National party leader John Swinney, and Sinn Féin vice-president Michelle O’Neill affirmed their nations’ right to seek independence. The memorandum states that no Westminster government has the right to block democracy by refusing a referendum if the public demands it.

O’Neill, who serves as First Minister in Northern Ireland’s power-sharing executive, called for an immediate referendum on Irish unity. Swinney also called for an immediate independence referendum in Scotland, while ap Iorwerth declined to give a timetable for Wales.

The signing followed recent remarks by US President Donald Trump, who said during a visit to Ireland that he would love to see a united Ireland and it may as well happen now. The comments drew sharp responses from unionist politicians and the UK government.

The memorandum is not legally binding but signals increased coordination among pro-independence parties. Support for Irish unity in Northern Ireland stands at 36%, according to recent polling, while the Good Friday agreement remains vague on the trigger for a border poll.

Sinn Féin is focused on next year’s Stormont assembly elections, where it is expected to remain the largest party despite a fall in support. The party has faced criticism over public services and infrastructure delivery.

Later on Monday, Swinney and ap Iorwerth signed the Cardiff Agreement, setting out shared priorities such as child poverty and economic growth. Swinney described it as an important moment in the history of devolution.