The European Union has urged Spain to analyze why citizens' faith in judicial independence has dropped from last year, following a report which ranks Spain as the fourth worst among the 28-member EU.

"The reasons for the decrease should be better analyzed on the domestic territory," said Věra Jourová, the European commissioner for justice. "It's up to Spanish experts to look into all figures and come with an explanation for this trend."

According to the study, 55% of Spaniards describe the independence of courts as "bad" or "really bad", with 40% of them attributing the lack of impartiality to political interferences.

Spanish courts rank fourth from the bottom in citizens' trust, only before Bulgaria, Slovakia and Croatia, and performing worst than courts in Italy and Slovenia.

The study also found that Spain's Supreme Court, where 12 Catalan politicians and activists are facing trial for their role in the independence bid, is the second European court with less female judges.