De Boer became a member of the House of Representatives after the resignation of Joop Bakker, taking office on 16 February 1972 serving as a frontbencher chairing the special parliamentary committee for Gambling Reforms and the special parliamentary committee for Fishing Zones Establishments and spokesperson for small business, the civil service, fisheries, culture, media and military personnel.

After the 1977 general election, the Christian Democratic Appeal and the People's Party for Freedom and Democracy (VVD) formed the Van Agt–Wiegel cabinet.

De Boer and several other CDA members of the House of Representatives were critical of the coalition agreement and formed an informal caucus in their own parliamentary group called the Loyalists [nl] that supported the cabinet only with confidence and supply.

After the 1981 general election, De Boer was appointed State Secretary for Culture, Recreation and Social Work in the Van Agt II cabinet, taking office on 11 September 1981.

De Boer retired from active politic and became active in the private sector and public sector and occupied numerous seats as a corporate director and nonprofit director on several boards of directors and supervisory boards (Stork B.V., Stichting Pensioenfonds Zorg en Welzijn, European Cultural Foundation, Intertrust Group Transnational Institute, Max Havelaar Foundation and the World Press Photo) and served on several state commissions and councils on behalf of the government (Stichting Pensioenfonds ABP, Advisory Council for Spatial Planning, Environmental Assessment Agency and the Social and Economic Council).