MADRID—The lower chamber of Spain's Parliament, responding for the first time to the Catalonia region's plan to hold a referendum on independence, passed a motion Thursday rejecting such a vote "categorically and clearly" by an overwhelming margin.

But in a sign of the gulf between Madrid and the Catalan capital of Barcelona, Catalonia took another baby step toward independence Thursday, announcing the creation of a tax-collection agency that it called the "embryo" for future fiscal autonomy. The regional...