<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 membership referendum, also known as the Referendum on the European Community (Common Market), the Common Market referendum and EEC membership referendum took place 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 "European Community" and the "Common Market" which it had entered on 1 January 1973 under the Conservative government of Edward Heath under the provisions of the Referendum Act 1975 . 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 ever to be held throughout the entire United Kingdom, and was the only national UK - wide referendum held in the 20th Century 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 . </P>

Who was prime minister when we joined the common market