From 1987 to 1988 Duquesne served as Minister of Education. In 1988 Duquesne was elected a member of the Belgian Senate. In 1990 Duquesne was made President of the PRL. In 1991 Duquesne was elected as a member of the Belgian Chamber of Representatives, re-elected in 1995 and 1999, and concurrently for a time served as a member of the Walloon Regional Council and the French Community Council (1991–1995). During this time he served as Quaestor (1995), Chairman of the Committee on Justice (1996–1999) and the Committee on Foreign Relations (1999) and Vice-President of the Chamber of Representatives and Chairman of the PRL-FDF parliamentary intergroup.