Spain's Constitutional Court has unanimously declared a vote on secession by the powerful northeastern region of Catalonia last November as unconstitutional.

The court ruled Tuesday that a law passed by the Catalan regional government allowing it to call such votes is also unconstitutional.

The court had ordered the suspension of the Nov. 9 vote while it studied a complaint from the central government.

But Catalonia pressed ahead, labeling the referendum an informal process so as to try to skirt the suspension order.

Prosecutors have since filed suits against Catalan regional President Artur Mas for staging the vote.

Catalan officials said that out of 6.3 million potential voters, 2.3 million cast ballots, with most favoring secession.

Mas now hopes to get backing for his independence push in regional elections in September.