Turp joined the Bloc Québécois, becoming that party's Political Affairs Committee president during Prime Minister Jean Chrétien's first term in office. He was defeated in the Papineau-Saint-Michelelectoral district in 1996 when he first attempted to become a federal Member of Parliament. He succeeded in 1997, becoming a member of the House of Commons of Canada for the Beauharnois—Salaberry riding. He left federal politics in 2000 after being defeated by Liberal Serge Marcil. In 2003, he moved to provincial politics under the Parti Québécois and was elected in the riding of Mercier on April 14. Turp became the party spokesman on international relations and sat on the Parliamentary Assembly of la Francophonie. In 2005, he proposed a project for a Quebec constitution and he signed the Manifeste pour un Québec solidaire. He has published many articles on Quebec sovereignty and its constitutional implications. Turp supported André Boisclair during the Parti Québécois' party leadership campaign in 2005, and was reelected in the 2007 election. He faced some criticism in 2008 as one of two MNAs, along with Pierre Curzi, who endorsed a controversial petition opposing Paul McCartney's performance at Quebec City's 400th anniversary celebrations. He was defeated in 2008 by Amir Khadir, co-leader of Québec solidaire. In 2011, Turp unsuccessfully ran for president of the Parti Québécois.
Publications
1995: L'Avant projet de loi sur la souveraineté : texte annoté, Cowansville, Les Éditions Yvon Blais.
2000: La nation bâillonnée : le plan B ou l'offensive d'Ottawa contre le Québec, Montreal, VLB éditeur.
2001: Le droit de choisir : Essais sur le droit du Québec à disposer de lui-même/The Right to Choose : Essays of Québec's Right to Self-Determination, Montreal. Éditions Thémis
2005: Nous, peuple du Québec : un projet de constitution du Québec. Sainte-Foy, Éditions du Québécois.
;Collaborations
1986: G. Beaudoin, Perspectives canadiennes et européennes des droits de la personne, Cowansville, Éditions Yvon Blais.
1995: Brossard, J. and D. Turp, L'accession à la souveraineté et le cas du Québec : conditions et modalités politico-juridiques, 2nd edition, Montreal, PUM.
1996: Debard, T., J. Schmidt, V. Nabhan and D. Turp, La régulation juridique des espaces économiques : interactions GATT/OMC, Union européenne et ALÉNA, Lyon, Centre Jaques-Cartier.
1997: Morin, J.-Y., Rigaldies and D. Turp, Droit international public : notes et documents, Montreal, Les Éditions Thémis, 3rd edition.
1998: Schabas, W. and D. Turp, Droit international, canadien et québécois des droits et libertés : notes et documents, Cowansville, Les Éditions Yvon Blais, 2nd edition.