When the issue of Britain joining the EEC was raised following Harold Macmillan’s opening of negotiations in July 1961, Hugh Gaitskell had no time for those who saw the issue as one of principle, whether they were passionate pro-Europeans like Roy Jenkins or passionate opponents like many on the left who saw it as ‘a kind of giant Catholic, capitalist conspiracy’. (All quotations come from Philip Williams’s magisterial 1979 biography of Gaitskell.) Everything would depend on the conditions.

In theory, Gaitskell and Macmillan’s conditions were the same: a complete rejection of European federalism and safeguards for Britain to retain an independent foreign policy and economic planning; safeguards for the Commonwealth, in particular the recently decolonised nations of the New Commonwealth; Britain’s partners in the European Free Trade Association to be ‘looked after’; and a reasonable deal for British agriculture (which signalled Gaitskell’s complete revulsion from the Common Agricultural Policy).

In April 1962, Jenkins invited Jean Monnet to address a meeting of Labour intellectuals. Monnet insisted that all problems could be solved if they committed themselves emotionally to a supra-national Europe. Gaitskell plied him with questions about the single market's practical effects, especially on the Third World. Monnet tried to evade such detail. ‘You must have faith,’ he protested. ‘I don't believe in faith,’ Gaitskell replied. ‘I believe in reason and you haven't shown me any.’ Jenkins was dismayed, believing Gaitskell was turning against the EEC, though in fact Gaitskell continued to sit on the fence and furiously denounced an anti-EEC paper from Transport House.

Gaitskell had a similar clash with the Belgian Socialist leader Paul-Henri Spaak, who shared Monnet's federalist vision. Spaak insisted that Europe's political reconciliation was the most important development in world politics. Gaitskell said he could share some enthusiasm for Europe but stopped well short of federalism. Meanwhile, he thought the EEC ‘parochially European’ and made it clear that he personally had more in common with North Americans. He also dismissed the Liberal notion that European integration was a question of moral idealism: the CAP, after all, was ‘one of the most devastating pieces of protectionism ever invented’.

He had strong feelings for Labour’s socialist friends in Europe who were keen on British entry. ‘The Communists,’ he pointed out, ‘naturally oppose our going in … because they believe it would strengthen the democratic forces of the West. They are right.’ From his correspondence with President Kennedy, the Americans concluded that he was ‘moderately in favour’ of entry, even though he inveighed against the ‘complete nonsense’ talked by both sides in the debate, and said he found the issue ‘always a bore and a nuisance’. But he returned always to the conditions. If Britain went in on the wrong terms, ‘history will never forgive us.’ The worst outcome of all would be Britain going into the EEC but having to retreat from it later, which would cause ‘a huge dislocation’.

Until July 1962, Gaitskell remained ‘reasonably hopeful’ of entry and was planning how ‘to handle the extreme anti-Marketeers’. At the beginning of August, however, he was shocked when Macmillan announced his provisional agreement on entry, which effectively gave way on every key point. Only then did Gaitskell realise that Macmillan and Ted Heath, who was responsible for the negotiations, had decided to go in on principle, whatever the cost. He wrote to Kennedy that he was ‘bitterly disappointed and indeed astonished. Had such terms been announced at the beginning of the negotiations, they would have been rejected out of hand by the British people.’ It was not even clear that Macmillan would resist European federalism. To Gaitskell that was the crunch: ‘It means the end of Britain as an independent nation … It means the end of a thousand years of history; it means the end of the Commonwealth.’

‘It seems certain’, he wrote to Kennedy, that the Tories ‘are shortly to launch a major propaganda campaign in favour of Britain's entry on broadly any terms … leading up to the General Election’. Heath, he said, ‘had been accepting anything to get in quickly’. As Gaitskell’s attitude hardened, he came under criticism from the quality press, all of it now pro-EEC. He was enraged:

We are now being told that the British people are not capable of judging the issue … the government knows best; the top people are the only ones who can understand it; it is too difficult for the rest … what an odious piece of hypocritical supercilious arrogant rubbish.

At the Labour party conference in October, Gaitskell denounced entry on the terms provided by Macmillan, provoking a huge ovation – though even then he hoped that Europe could be ‘argued out of its protectionism’. By this time he was getting messages from France to the effect that De Gaulle would not accept federalism either, and that he was cool to British entry. On 11 January 1963, Macmillan noted that once negotiations were successfully concluded, ‘we can let loose a great pro-European propaganda’. Three days later De Gaulle announced he would veto British entry and four days after that Gaitskell died.