The Common Market referendum 5 June 1975 in the United Kingdom to gauge support for the country's continued membership of the European Community and the Common Market — which it had entered two-and-a-half years earlier on 1 January 1973 under the Conservative government of Edward Heath. The Labour Party's manifesto for the October 1974 general election had promised that the people would decide through the ballot box whether to remain in the EC.
This was the first national referendum ever to be held throughout the United Kingdom, and would remain the only UK-wide referendum until the 2011 referendum on the Alternative Vote system was held thirty-six years later.
The electorate expressed significant support for EC membership, with 67% in favour on a national turnout of 64%. The referendum result was not legally binding; however, it was widely accepted that the vote would be politically binding on all future Westminster Parliaments.
The February 1974 general election had yielded a Labour minority government, which then won a majority in the October 1974 general election. Labour pledged in its February 1974 manifesto to renegotiate the terms of British accession to the EC, and then to consult the public on whether Britain should remain in the EC on the new terms, if they were acceptable to the government. The Labour Party had historically feared the consequences of EC membership, such as the large differentials between the high price of food under the Common Agricultural Policy and the low prices prevalent in Commonwealth markets, as well as the loss of both economic sovereignty and the freedom of governments to engage in socialist industrial policies, and party leaders stated their opinion that the Conservatives had negotiated unfavourable terms for Britain.
The referendum debate and campaign was an unusual time in British politics and was the third national vote to be held in seventeen months. During the campaign, the Labour Cabinet was split and its members campaigned on each side of the question, an unprecedented breach of Cabinet collective responsibility.
The referendum did temporarily achieve Harold Wilson's ambition to bring the divided Labour Party together on the European issue