All 72 separatist lawmakers – the majority in the northeastern region's parliament – voted for the resolution aimed at creating an independent republic by 2017.
A total of 63 MPs voted against the nine-point motion which includes a solemn declaration calling for “the beginning of the creation of an independent Catalan state in the form of a republic”.
— eldiario.es (@eldiarioes) November 9, 2015
The resolution has the backing of Catalan president Artur Mas' Together for Yes coalition and the smaller far-left separatist CUP party, which together have a majority in the regional assembly with 72 seats of the 135 seats.
But Spanish Prime Minister Mariano Rajoy and his staunchly anti-independence Popular Party (PP) have the backing of the main opposition Socialists and new, popular centre-right group Ciudadanos.
“I was born in Catalonia and I want to keep living here,” said Xavier García Albiol of the ruling PP party during a debate before Monday's vote.
“While you are spending your time and efforts to break up Catalonia from the rest of Spain, 600,000 Catalans go out on the street every day to look for work,” said the politician born to a Catalan mother and an Andalusian father, referring to pro-independence lawmakers.
“While you are dedicating your time to creating state structures, 1.5 million Catalans live in precarious conditions.”
There have long been demands for greater autonomy in Catalonia, a region of 7.5 million people with its own language that accounts for a fifth of Spain's economic output.
These calls have intensified in recent years, in tandem with the country's economic crisis.
A 2010 decision by Spain's Constitutional Court to water down a 2006 statute giving the region more powers has added to the growing pressure for secession.
Rajoy said on Monday afternoon his government would challenge in court the vote by Catalonia's parliament.
He told reporters that after an emergency cabinet meeting on Wednesday, “I will sign a recourse (to the Constitutional Court) of unconstitutionality and will ask for… the immediate suspension of this initiative and all its possible effects”.
If the court accepts the government's appeal as is expected, the Catalan resolution will be automatically suspended until judges hear arguments and make their decision.
Rajoy's government in September boosted the powers of the Constitutional Court to allow it to quickly suspend leaders who disobey its orders, in a move aimed directly at Catalonia.
The government has also raised the possibility of invoking article 155 of the Spanish constitution, which allows Madrid to supersede the authority of a regional government that is acting outside the law or cut off its funding.
But those who crafted the declaration had anticipated this, and the resolution states that the secession process will not be subject to decisions made by Spanish institutions, including the court.
While not legally binding, the text calls on the regional assembly to start working on legislation within 30 days to create a separate social security system and treasury, with a view of complete independence as early as 2017.
“With this resolution, we are solemnly kicking off the construction of a state,” Raul Romeva of Together for Yes told regional lawmakers on Monday.
— Junts pel Sí (@JuntsPelSi) November 9, 2015
Catalonia tried to hold an official referendum on independence last year, but judges ruled it was against the constitution, arguing that all Spanish people have the right to decide on matters of sovereignty.
The region pressed ahead anyway and held the referendum, although it was purely symbolic in nature.
Turnout was 37 percent, of which over 80 percent voted in favour of independence.
“A referendum would be the ideal tool, but the Spanish government blocked it. We have no other option but unilateral action,” CUP lawmaker Albert Botran told news agency AFP.
While Catalan separatist parties won a majority of seats in the regional parliament in September polls, they failed to win a majority of all votes cast – a fact emphasized by their opponents.