The European Economic Community (EEC) was formed in 1957. The United Kingdom (UK) first applied to join in 1961, but this was vetoed by France. A later application was successful and the UK joined in 1973; a referendum two years later on continuing membership resulted in 67% approval. Political integration gained greater focus when the Maastricht Treaty established the European Union (EU) in 1993, which incorporated (and after the Treaty of Lisbon, succeeded) the EEC . Britain has voted to leave the European Union, forcing the resignation of Prime Minister David Cameron and dealing the biggest blow since World War Two to the European project of forging greater unity.