"We represent a sovereign parliament which wants to represent a free people. We are transitioning from a regional parliament with limited powers to a national parliament with full capabilities," said Carme Forcadell, the parliament's new president.
"Long live the Catalan Republic!" declared Forcadell, the former leader of a pro-independence movement that contested a regional election last month under the "Junts pel si" (Together for Yes) banner of separatist parties.
She has been heavily criticised by political groups that reject full independence for Spain's regional economic powerhouse, home to 7.5 million people, who accuse her of representing a vocal minority only.
The pro-independence camp fell short of winning a majority of votes, capturing 48 percent of all ballots, and handing its adversaries in the central government in Madrid a strong argument to resist the push for independence.
The opening of the parliament comes ahead of the first round of elections to choose the regional president on November 9th, with incumbent Artur Mas hoping for re-election.
But Mas faces an uphill battle: he is seeking the support of the leftist Popular Unity Candidacy (CUP), whose 10 seats would give the pro-secession parties an outright majority in the assembly, but they are refusing due to his austerity politics and corruption allegations against his Convergence party.
The current party treasurer, along with its former treasurer, were detained on suspicion of charging commissions in exchange for public works contracts last week.
The impasse could leave the region without a leader until December 20th, when a general election will be held that could see the Catalan question take centre stage as Prime Minister Mariano Rajoy seeks re-election for his conservative Popular Party.
Rajoy said Monday the Catalan push for independence showed "disloyalty to the constitution", arguing the Spanish constitution does not allow any region to break away and vowing to ensure that the law is respected.