The Government of Ireland Act 1920 provided for an Irish Council, but these provisions had never been adopted. The Unionists were furious at any “interference” by the Republic of Ireland in its newly created region. In 1973, following an agreement on the formation of an executive, an agreement was reached on the reintroduction of an Irish Council to promote cooperation with the Republic of Ireland. Between 6 and 9 December, discussions took place in the town of Sunningdale in Berkshire between British Prime Minister Edward Heath, Irish Prime Minister Liam Cosgrave and the three pro-agreement parties. The 1998 Good Friday Agreement (GFA), on which the current system of decentralisation in Northern Ireland is based, is similar to that of Sunningdale.  Irish politician Séamus Mallon, who participated in the negotiations, called the agreement “Sunningdale for slow learners.” This claim has been criticized by political scientists such as Richard Wilford and Stefan Wolff. The former said that “it`s… [Sunningdale and Belfast] have considerable differences, both in terms of the content and circumstances of their negotiation, implementation and implementation.”  On Sunday, December 9, 1973, a communiqué announced the agreement at the Sunningdale talks; this release should be known as the Sunningdale Agreement. These issues were resolved, at least in theory, by the Sunningdale Agreement.
This agreement, signed in December 1973, created three political bodies: a proportionally elected Northern Ireland Assembly, an executive government with power shared by nationalists and unionists, and a “Council of Ireland” composed of delegates from Northern Ireland and the Republic of Ireland. In signing the agreement, the Irish Government fully accepted and stated that the status of Northern Ireland could not change until the majority of the northern population wished to change that status. The British government has declared that it is and will remain its policy of supporting the wishes of the majority of the people of the North. The current status of Northern Ireland is that it is part of the United Kingdom. If, in the future, the majority of Northern Ireland expresses a desire to see a united Ireland, the British Government would support this wish. On Monday, 8 April 1974, Merlyn Rees, then Sate Minister for Northern Ireland, met with representatives of the Ulster Workers` Council (UWC). The meeting did not reach an agreement. [At this stage, the UWC was not considered a serious threat to the future of the executive, mainly because of the failure of previous work stoppages of the Loyalist Workers Association (LAW) and the apparent low support for protests against the Sunningdale agreement.] While moderate Unionists could tolerate a power-sharing cabinet, they could not support Ireland`s proposed council. The Unionists, still suspicious of Dublin, saw the Council as an important step towards the reunification of Ireland. The nationalists supported the idea.
In March 1974, trade union supporters withdrew their support for the agreement and asked the Republic of Ireland to repeal Articles 2 and 3 of its Constitution (these articles would not be revised until after the 1998 Good Friday Agreement). In the General Elections of February 1974, the United Ulster Unionist Council, a coalition of anti-Sunningdale unionists, won 11 out of 12 constituencies in Northern Ireland. Only West Belfast has returned a pro-agreement MP. On 21 November, an agreement was reached on a voluntary coalition of pro-agreement parties (contrary to the provisions of the Belfast Agreement, which defines Hondt`s method for electing ministers over the main parties in the Assembly).