MADRID (AP) — Spain says it has appealed to the Constitutional Court to block a measure passed by the regional parliament of Catalonia that would allow it to fast-track a declaration of independence if its voters choose to secede from Spain in a planned Oct. 1 referendum.

The legal challenge is the latest by the central government in Madrid to block the vote.

Announcing it Friday, Prime Minister Mariano Rajoy reiterated there would be no referendum because it was unconstitutional.

The Barcelona-based Catalan Parliament hopes the measure approved Wednesday will allow the wealthy, northeastern region to declare independence within 48 hours of the referendum.

Polls consistently show the 7.5 million Catalans are evenly divided on secession, but a majority wants a referendum.

The issue has embittered relations between Spain and Catalonia for years.