Brexit: British withdrawal from the European Union

In 1975, the United Kingdom held a referendum on whether the UK should remain in the EEC. All of the major political parties and mainstream press supported continuing membership of the EEC. However, there were significant splits within the ruling Labour party, the membership of which had voted 2:1 in favour of withdrawal at a one-day party conference on 26 April 1975. On 5 June 1975, the electorate were asked to vote yes or no on the question: "Do you think the UK should stay in the European Community (Common Market)?" Every administrative county in the UK had a majority of "Yes", except the Shetland Islands and the Outer Hebrides. In line with the outcome of the vote, the United Kingdom remained a member of the EEC.

In 2012, Prime Minister David Cameron rejected calls for a referendum on the UK's EU membership, but suggested the possibility of a future referendum. Under pressure from many of his MPs and from the rise of UKIP, in January 2013, Cameron announced that a Conservative government would hold an in-out referendum on EU membership before the end of 2017, on a renegotiated package, if elected in 2015.

The Conservative Party won the 2015 general election with a majority. Soon afterwards the European Union Referendum Act 2015 was introduced into Parliament to enable the referendum. Despite being in favour of remaining in a reformed European Union himself, Cameron announced that Conservative Ministers and MPs were free to campaign in favour of remaining in the EU or leaving it, according to their conscience. This decision came after mounting pressure for a free vote for ministers. In an exception to the usual rule of cabinet collective responsibility, Cameron allowed cabinet ministers to campaign publicly for EU withdrawal.

On the morning of 24 June, the result from the vote was that the United Kingdom had voted to leave the European Union by 52% to 48%.