[1] De Koning joined the Dutch resistance against the German occupation in September 1943, at the time barely 17 years old.

After the 1977 general election, De Koning was appointed Minister for Development Cooperation in the Van Agt–Wiegel cabinet, taking office on 19 December 1977.

After the 1981 general election, he was appointed Minister of Agriculture and Fisheries in the Van Agt II cabinet taking office on 11 September 1981.

De Koning continued to be active in politics and in December 1989 was nominated as a member of the Council of State on 1 January 1990.

De Koning also became active in the public sector as non-profit director and serves on several state commissions and councils on behalf of the government, and worked as a distinguished professor of Social geography at the University of Groningen from January 1991.