BARCELONA, Spain (AP) — Catalonia’s separatist movement has suffered its biggest rift since it became the leading political force in northeast Spain for the past decade after the junior member of its ruling coalition abandoned the region’s government.

The Together for Catalonia party announced Friday that it was leaving the Barcelona-based government headed regional President Pere Aragonès of senior coalition member Republican Left of Catalonia. The move came a week after its leading member in the Catalan Cabinet was fired by Aragonès.

The official breakup ends a partnership that had existed between the two main pro-secession parties since they joined forces for a regional election in 2015. They had the shared goal of boosting the separatists’ hold on power in the wealthy region, where many resident feel different from the rest of Spaniards.

“If we talk about winners or losers, Together for Catalonia wins and Pere Aragonès loses. He loses because he thought he could lead a coalition government, and today that is proven not to be true,” Together for Catalonia secretary general Laura Borras said. “From today, we join the opposition … we don’t want to be in any government that does not advance toward independence.”

Aragonès, who came to power last year, has said his party will still rule in the minority. Still the political divorce is a blow to the region’s separatist push, which has been floundering to find its way forward five years after its unsuccessful 2017 secession bid that landed several of its leaders in jail or on the run in Europe.