The belief was that in removing non-tariff barriers to cross-border intra-Community trade and investment such measures would provide the twelve Member States a broad economic stimulus.

To facilitate their removal, the SEA reformed the Community legislative process both by introducing the cooperation procedure and by extending Qualified Majority Voting to new areas.

The Danish parliament rejected the Single European Act in January 1986 after an opposition motion calling for the then unsigned document to be renegotiated was passed by 80 votes to 75.

While completion of the Community's internal market in 1992 might not "be enough to bring unemployment down to the low-water mark reached just before the [1973] oil crisis", EC Commission President Jacques Delors was confident that it would be "enough to reverse the trend".

[12] Given that the model of full-time, regular employment continued to underlie social-security arrangements, this suggested the possibility of serious losses in welfare and equity.

A second reservation with regard to the employment benefits of the Single Market was that projections tended to assume a reversal, or at least easing, of the then relatively restrictive macro-economic policies of the member states.

The Cecchini's Reports higher medium-term estimate of 4.4 million additional jobs resulting from the removal of the remaining barriers to intra-Community trade assumed that chief among the benefits of comprehensive trade liberalisation would be a spontaneous easing of inflationary pressures and external balance of payments constraints, and that the subsequent "room for manoeuvre" would be "exploited" by a resort to "expansionary economic policies".

[13] The SEA committed the Member States to promote "the convergence of economic and monetary policies" necessary for European Currency Union (ECU).

[14] The EMS linked the currencies of participating states, and committed their governments to fiscal and monetary policies sufficiently tight to contain inflation and prevent large exchange rate fluctuations.

It was Thatcher's nominee to the Delors Commission, Lord Cockfield, who, as the commissioner responsible for the Single Market, drew up the initial White Paper.

Moving beyond the tariff-free commitment of the Common Market, the act would dismantle the "insidious" barriers to intra-Community trade posed by "differing national standards, various restrictions on the provision of services, [and the] exclusion of foreign firms from public contracts".

[16]In promoting the Single Market, in the SEA Thatcher made compromises that a growing body of opinion in her Conservative Party were to regard as fatal.

While presuming that Britain would remain "part" of a "European free trade zone from Iceland to the Russian border",[18] the official Vote Leave campaign and its allies proved victorious in the "Brexit" referendum of June 2016.