The EEC question was the issue that would cause Powell to leave the Conservative Party on 23 February 1974, as Conservative Prime Minister, Edward Heath, had taken Britain into the EEC on 1 January 1973 without an electoral mandate from British voters. Powell leaving the Conservative Party came just 5 days before the general election took place. After his resignation, Powell then shocked his former Conservative colleagues by calling on the public to vote for the Labour Party, as Labour were offering a referendum on EEC membership. Powell placed the EEC question above all other matters since it eroded national sovereignty in an unprecedented way that had not been not known since the English Reformation; EEC law had primacy over law made in the British Parliament, which Powell considered to be the true representation of the British nation, with the British monarch as its head.