The Spanish government says it will challenge a recent declaration by lawmakers in Catalonia that the region is a sovereign entity.
Deputy Prime Minister Soraya Saenz de Santamaria says Friday that the appeal to the Constitutional Court is based on the opinion of the Council of State consultative body, which says the declaration is unconstitutional.
Though the January declaration is largely symbolic it potentially paves the way for a proposed referendum on Catalonia's right to decide its relationship with Spain.
Catalonia is the wealthiest region of Spain and in Barcelona has one of Europe's most high-profile cities. The regional government's president Artur Mas accused the government of being anti-democratic.
Polls show Catalans are evenly divided over independence, though a majority oppose it if it means exiting the European Union.