The explicitly federal implications of the EEC made it superficially unattractive for the rest of Europe. A variety of political, economic or security reasons confined the supranational course initially to a limited group of countries; albeit a group that comprised more than half of Western Europe's output and foreign trade. Nonetheless the outsiders still constituted a sizeable market of considerable sophistication and one that had shared with the Six the same pan-European movement towards commercial liberalisation and growing interdependence. Among smaller trading economies as Denmark, Sweden and Switzerland in particular there existed the same drive towards a further relaxation of protectionism as had motivated the Benelux countries. This drive was reinforced by the fear of what might happen once the mutual preferences, implied by the formation of the customs union by the Six, began to take effect. The government of the United Kingdom was particularly concerned about the possibility of an economic division of Europe and, at the end of 1956, tried to neutralise the effect of EEC preferences with a proposal for a wider industrial free trade area to be constructed inside the OEEC.

The initiative was launched at a particularly testing moment for the Six since the common market negotiations had still to be concluded and the outcome to be ratified by national parliaments. The Commission of the EEC itself did not begin work until January 1958. If the free trade area offered the non-member states a solution for their dilemmas, for the Six it posed a distinct threat. Distrust of British motives suffused the following negotiations but there were more prosaic reasons why the Six were reluctant to embrace the UK initiative. For example, the French, in the final stages of the common market negotiations, obtained a set of favourable conditions and safeguards that they could not replicate in the free trade area. Moreover, the French, Italians and Dutch had obtained some ‘compensation’ for opening their industrial markets through the prospect of a common agricultural policy, but agriculture was exempted from the British plan. Finally, those who hoped that the Community institutions would rapidly develop in a federalist direction were worried whether their energies might not be dissipated by the free trade area.