On 23 June 2016, a referendum, commonly referred to as the EU referendum or the Brexit referendum, took place in the United Kingdom (UK) and Gibraltar to ask the electorate whether the country should remain a member of, or leave, the European Union (EU). It was organised and facilitated through the European Union Referendum Act 2015 and the Political Parties, Elections and Referendums Act 2000. The referendum resulted in 51.9% of the votes cast being in favour of leaving the EU. The referendum was legally non-binding due to the ancient principle of parliamentary sovereignty as the enabling legislation only specified that a referendum should be held; however, the Conservative government of the time which was led by the then Prime Minister David Cameron promised to implement the result.
Since 1 January 1973 the United Kingdom had been a EU member state since it first joined the then European Communities (EC), principally the European Economic Community (EEC) or Common Market, the forerunner to the European Union, along with the European Coal and Steel Community (ECSC), and the European Atomic Energy Community (EAEC or Euratom) and throughout the time since joining membership of the bloc and its constitutional implications for the UK (in particular the effect of the European Communities Act 1972) had been a topic of debate. A referendum on continued membership of the Communities to try and settle the issue was held in 1975, with 67.2% of the votes cast in favour of the UK remaining a member. However during the next forty one years between 1975 and 2016 as European integration deepened from one that was originally economic in nature into a political project no further referendums on the issue of Europe were held with subsequent EC/EU treaties and agreements being ratified only by the UK Parliament.
Following the surprise Conservative Party victory at the 2015 general election as a main manifesto pledge, the legal basis for the EU referendum was established through the European Union Referendum Act 2015. Britain Stronger in Europe became the official group campaigning for the UK to remain in the EU, and was endorsed by the Prime Minister David Cameron and Chancellor George Osborne. Vote Leave was the official group campaigning for the UK to leave the EU, and was fronted by Conservative MPs Boris Johnson and Michael Gove along with Labour MP Gisela Stuart. Other campaign groups, political parties, businesses, trade unions, newspapers and prominent individuals were also involved, with both sides having supporters from across the political spectrum. Parties in favour of 'remain' included Labour, the Liberal Democrats, the Scottish National Party (SNP), Plaid Cymru and the Green Party; while the UK Independence Party (UKIP) campaigned in favour of leaving the European Union; and the Conservative Party remained neutral. In spite of the official positions of the Conservative Party and Labour, both parties allowed their MPs to publicly campaign for either side of the issue.
Immediately after the result, financial markets reacted negatively worldwide, and Cameron announced that he would resign as Prime Minister and Leader of the Conservative Party, having campaigned unsuccessfully to remain in the European Union. It was the first time that a national referendum result had gone against the preferred option of the UK Government. Cameron was succeeded by Theresa May on 13 July 2016. Labour leader Jeremy Corbyn also faced a leadership challenge as a result of the EU referendum. On 29 March 2017, the United Kingdom gave formal notice of intent to withdraw from the EU.
Background
The European Communities were formed in the 1950s the European Coal and Steel Community (ECSC) in 1952, and the European Atomic Energy Community (EAEC or Euratom) and European Economic Community (EEC) in 1957. The EEC, the more ambitious of the three, came to be known as the "Common Market". The UK first applied to join them in 1961, but this was vetoed by France. A later application was successful, and the UK joined in 1973; two years later, the first ever national referendum on continuing membership resulted in 67.2% approval, with a 64.62% turnout. 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 European Communities.
Growing pressure for a referendum
Prior to the 2010 general election, the then Leader of the Conservative Party and Leader of the Opposition David Cameron promised a referendum on the Lisbon Treaty, which he backtracked on after all EU countries had ratified the treaty before the election.