Plaid Cymru says that British people should be allowed to keep hold of EU citizenship allowing them to travel, live and work freely in Europe even after the UK leaves the European Union.
The party has written to the Prime Minister urging her to use Brexit talks to negotiate continuing citizenship agreements with the EU or to develop a new model of 'Associate European Citizenship.'
Ahead of a debate that Plaid is leading in the House of Commons later, it's published expert legal advice arguing that 'it would be illegal under both European law and international law, for citizens to be stripped of their EU citizenship.'
Brexit spokesperson Hywel Williams said:
Plaid MPs think their debate could lead to a vote and although it wouldn't be binding it could mean a defeat for the UK Government which has a policy of abstaining on opposition day debates because it lacks a majority in the Commons.
A UK Government spokesperson says that leaving the EU will mean relinquishing EU citizenship and that there will be new arrangements for travel and work.
Supporters of Brexit say that by focussing on an attempt to keep hold of EU citizenship, Plaid has demonstrated that it's 'hasn't quite grasped why people voted to leave the European Union.'
Matthew MacKinnon, Director of the Centre for Welsh Studies think tank says Plaid is clinging to 'a vision of a Europe without borders [which] is now a minority, fringe view.'