The United Church of Canada has always sought the widest possible union of Christian communions, and a Committee on Negotiations with other Communions with a view to Union was instituted in 1926 at the first General Council. Apart from negotiations with some smaller Churches leading to unions (Wesleyan Methodist Church of Bermuda, 1930 and the Evangelical United Brethren, 1968), most of the union activity had been directed towards an organic union with the Anglican Church of Canada and the Church of Christ (Disciples). Beginning in 1943 the United Church Commission on Reunion, the successor body to the Committee on Negotiations, entered into earnest consultation with the Anglican Church which continued for thirty years.
The United Church Commission on Reunion was made up of smaller subcommittee groups of fifteen members, and also five representatives to report to the fifteens, which held joint meetings with corresponding Anglican Committee on Reunion members. In 1950, the Commission was renamed the Commission on Union and by 1959, subcommittees were organized to include discussions with the Evangelical United Brethren. By 1968, the Evangelical United Brethren formally joined the United Church of Canada.
In 1969, the Christian Church (Disciples of Christ) in Canada formally joined union talks alongside the United and Anglican Churches. Generally, talks up to this point attempted to formulate a general basis of union, although study guide materials were created. In 1958, a Montreal sub-committee produced “Outline Scheme of Union,” which became an initial working paper for a basis of union, however, such development never arose at the national level. While cooperation continued along local and regional lines, union development stalled until the mid-1960s when the “Principles of Union” put forth by the joint union committees was officially accepted by the Anglican church of Canada in 1965 and the United Church in 1966. Thus, in 1967, the General Commission was established along with five special commissions focusing on their respective fields: Church in the World, Legal, Constitution, Liturgical, and Doctrine. Reverend Robert B. Craig of the United Church and Canon Ralph Latimer of the Anglican Church acted as Executive Commissioners. Besides those on the commission, critiques and opinions on matters of union were openly sought after from members of various denominations and theological backgrounds as part of the consultation process. International and ecumenical perspectives were also actively incorporated into the General Commission, including the World Council of Churches and foreign church bodies.
After initially releasing drafts and seeking input, the General Commission formally endorsed their document, the “Plan of Union,” in November of 1972 and presented to the churches in February of 1973. This officially ended the General Commission. The Committee on Church Union and Joint Mission (CUJM), led by Rev. Craig, took over continued union collaboration and revisions of the Plan of Union through to 1974. In early 1975, however, the Anglican Church rejected this basis of union, never reaching a congregational vote, and withdrew from joint union work. Discussions between the United Church and the Christian Church (Disciples) continued through the Joint National Committee on Union Negotiations until talks ended in 1985.