He was re-elected in 1988 federal election, only to leave the Progressive Conservative party on 26 June 1990 following the implosion of the Meech Lake Accord. In December that same year he would join the separatist Bloc Québécois party in Parliament.
Leblanc won another election in Longueuil riding in 1993. But in 1997, he left the Bloc Québécois and sat as an "independent sovereigntist" in the House of Commons. He did not seek re-election when the 36th Canadian Parliament ended later that year. In his varied Canadian political career, Leblanc served in the 33rd, 34th and 35th Canadian Parliaments.