Quim Torra, a close ally of former leader Carles Puigdemont, fell short of being elected the new Catalan leader by two votes.
Catalan pro-independence parties failed on Saturday for a fourth time to elect a regional leader, 10 days before the deadline to form a government or hold a new election.
Quim Torra, a close ally of former leader Carles Puigdemont, needed 68 votes to be elected but obtained only 66. However, Torra could still be elected in a second round of voting to be held on Monday in which only a simple majority in the 135-seat regional parliament is needed, provided the far-left CUP party can be persuaded not to vote against his candidacy.
The CUP, whose four parlementarians abstained in the vote on Saturday, will meet on Sunday to decide how it will vote in the second round.
Backing unilateral independence over the negotiated exit favoured by larger separatist parties, the CUP has previously broken ranks with the pro-independence block.
Catalonia has been in political limbo since December last year when pro-independence parties won early elections called by the central government.
Madrid invoked special powers to take direct control of Catalonia in October after the region declared independence. The wealthy, populous region has been administered by the central government ever since.
Catalan lawmakers must pick a leader to form a government by May 22 to avert further elections, following a standoff during which separatist politicians put forward candidates who were blocked by the courts for being either abroad or in jail, among them Puigdemont.
Addressing the Catalan parliament on Saturday, Torra, a staunch supporter of secession, vowed to work towards a Catalan republic and referred to Puigdemont as the legitimate leader of the region.
Torra also reiterated his openness to dialogue with Madrid, as well as calling on the EU to oversee negotiations.
The Spanish government said Torra’s speech was "confrontational".
"Any illegality will be corrected and any violation of our constitutional framework will be responded to," it said in a statement.