Harmel was elected to the Belgian parliament for the newly formed Social Christian Party in 1946. From 1950 to 1961 he served in a variety of government ministerial posts, including for education, justice, public services, and culture.
After serving as premier from July 1965 to March 1966, Harmel was named minister of foreign affairs in March 1966, a position he held until January 1973. Building on the policies of his predecessor, Paul-Henri Spaak, Harmel devised a foreign policy that combined strong Western military defenses with cooperation and rapprochement with the Eastern bloc. In December 1966 he gained approval from the North Atlantic Treaty Organization (NATO) for a multilateral appraisal of the alliance's future role, which resulted in the Harmel Report of December 1967. The report fine-tuned NATO's role and objectives and remained an important pillar of Atlantic policies throughout the Cold War. On the occasion of the report's twentieth anniversary in 1987, Harmel received the Atlantic Award for his service to the Atlantic Alliance.
In the late 1960s, Harmel forged contacts with his East European counterparts, particularly in Poland, to tackle contentious arms control issues such as the freezing of conventional and nuclear forces in Central Europe. He was an early advocate of mutual and balanced force reductions between East and West and of a conference for security and cooperation in Europe. Harmel's work made Belgium an influential player in international politics in the late 1960s and early 1970s. Harmel lives in Brussels and still comments on current affairs.
Haftendorn, Helga. "The Adaptation of the NATO Alliance to a Period of Détente: The 1967 Harmel Report." Pp. 285–322 in Crises and Compromises: The European Project 1963–1969, edited by Wilfried Loth. Baden-Baden: Nomos, 2001.