The total results of the referendum on UK membership in the European Union, which was the result of a vote of 52% of the British exit from the Union, showed that the European project, which is understood as a process of political integration within the European Union, has become unstable and insecure. The economic crisis and new crises such as immigration and the common market, as well as the thought of some countries to secede from the United Kingdom. There are also new discussions about the European project and its future stability, as this British decision affects the European Union significantly and the conditions of the Union's work and future, and the Brexit will damage the cohesion, trust and international reputation of the European Union. There is no doubt that the current situation is the most serious crisis in the history of European integration, where the vote for the "Brexit" sent shocks to all over the world, especially the European continent, shook financial markets and revive global discussions on the viability of the European Union in the long term. The paper will analyze the effects on Scotland, Northern Ireland and Wales.