<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The United Kingdom European Communities referendum of 1975, also known as the Common Market referendum and EEC membership referendum was non-binding referendum held on 5 June 1975 in the United Kingdom to gauge support for the country's continued membership of the European Communities (EC)--often known at the time as the "Common Market"--which it had entered on 1 January 1973 under the Conservative government of Edward Heath . Labour'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 . </P> <P> This was the first national referendum to be held throughout the entire United Kingdom, and remained the only UK - wide referendum until the 2011 referendum on alternative voting was held thirty - six years later and was the only referendum to be held on the UK's relationship with Europe until the 2016 referendum on continued EU membership . 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 the final say on the matter . In a 1975 pamphlet, the then Prime Minister Harold Wilson said: "(...) I ask you to use your vote . For it is your vote that will now decide . The Government will accept your verdict ." The pamphlet also said: "Now the time has come for you to decide . The Government will accept your decision - whichever way it goes ." </P>

Who was prime minister when britain joined the common market