The Conservative Prime Minister Edward Heath took the UK into the European Economic Community (EEC) in January 1973 after membership had been blocked on 2 previous occasions (vetoed in 1961 and 1969 by Charles de Gaulle). This brought the total number of members to 9 with Ireland and Denmark joining at the same time.
In 1975, the Labour prime Minister, Harold Wilson called a referendum for the public to decide whether the UK should remain as members of the EEC.
The question on the ballot paper was
“Do you think the United Kingdom should stay in the European Community (the Common Market)?”
The referendum was held on 5 June 1975.
There was a turnout of 64.03% from a registered electorate of 40,456,877.
67.2% voted in favour of staying in the EEC and 32.8% voted against.
More information can be found at the House of Commons Library in a briefing paper prepared in July 2015 The 1974-75 UK Renegotiation of EEC Membership and Referendum.
The Keep Britain in Europe campaign had the support of all the major political parties although Government ministers were allowed the freedom to differ from the party line and follow their consciences.
3 pamphlets were distributed to households in the UK one from the Government (in favour of remaining), one from the Yes campaign (in favour of remaining) and 1 from the No campaign (in favour of leaving).
Copies of the text used in these documents can be found at:
Government recommendation in Britain’s New Deal in Europe
Britain in Europe campaign Referendum on the European Community (Common Market) Why you should vote YES
The Conservative party also produced a separate guide calling for the UK to remain in the EEC.
Copies of the actual original pamphlets are reproduced at The 1975 Common Market Referendum Campaign Documents