In June 1974, in a letter to the Executive of the Carmarthen Constituency Labour Party, he warned of the dangers of the ever leftward drift of the party, saying: "I cannot any longer conceal my acute concern about some developments in the Labour Party which will in my view not enhance the prospects of the Labour Party and will also affect the longer term unity of the Labour Movement. I happen to believe strongly in the principles of Social Democracy." Jones lost his seat back to Evans by 3,640 votes at the October election of that year. When, in 1975, Prime Minister Harold Wilson held a referendum on Britain's membership of the European Economic Community (EEC), Jones was the Campaign Organiser in mid/west Wales for a 'Yes' vote.