The parliament has been split, as have most state institutions, since soon after it was elected in 2014, as Libya broke between warring factions in the east and west.
Libya's prime minister-designate has urged lawmakers to vote for his new government in the first reunited session of parliament in years that the UN hailed as "historic.
A total of 132 members of the 188-strong House of Representatives gathered to vote on interim premier Abdul Hamid Dbeibah's cabinet line-up, a crucial step toward December elections and stability after a decade of violence.
The UN mission in Libya praised Monday's meeting for "convening a reunified session after many years of divisions and paralysis."
Noting a "significant number" of lawmakers taking part, the UN said it "represents a critical step in unifying the country and preparing it to hold democratic national elections."
"This opportunity to open a new chapter for Libya should not be missed," it said in a statement.
If approved, it would replace the Tripoli-based Government of National Accord headed by Fayez al Sarraj, and a parallel eastern-based administration backed by strongman Khalifa Haftar.
"I call on deputies not to miss the chance to unify parliament with this meeting today ... so as to allow the government to immediately accomplish the difficult tasks" ahead, Dbeibah said.
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Decade-long violent turmoil
Libya descended into chaos after dictator Muammar Gaddafi was toppled and killed in a 2011 NATO-backed uprising that has seen rival forces vying for power in the oil-rich North African country.
A UN-supervised process aims to unite the country after a ceasefire reached last October between two rival administrations, each backed by foreign forces, based in the east and west of the country.
The 188-strong House of Representatives met in the coastal city of Sirte, the hometown of Gaddafi, located halfway between Tripoli, where the UN-recognised government is based, and the east, seat of a rival administration.
Prime minister-designate Abdul Hamid Dbeibah was elected in February at a UN-sponsored dialogue attended by a cross-section of Libyans to steer the country toward the scheduled December 24 polls.
His interim government faces the daunting challenge of addressing the grievances of Libyans, from a dire economic crisis and soaring unemployment to crippling inflation and retched public services.
Dbeibah, a billionaire businessman, submitted his 33-member cabinet line-up to parliament for approval last week, without publicly revealing any names.
An interim three-member presidency council, selected alongside prime minister Dbeibah last month, is to head the new unity administration.
If deputies fail to endorse the government on Monday, a new vote must take place, and Dbeibah has until March 19 to win approval for his cabinet.
But hurdles have emerged in the run-up to the vote, including allegations of vote-buying during the process to elect Dbeibah.
They centre on claims in a confidential report by UN experts that at least three participants were offered bribes of hundreds of thousands of dollars in November.
'Climate of tension'
Libyans have also taken to social networks to decry the size of the proposed government.
Many have criticised Dbeibah's decision to set up a cabinet with 33 ministers and two deputy premiers, saying a government due to rule just until December does not need to be so big.
The Sarraj government has only 26 portfolios.
Dbeibah has defended himself, saying he wanted to form a government that was "balanced" and "really representative of all the Libyan people" and major regions.
To reflect that, he said, seven key portfolios would be handed to figures from Libya's three main provinces in the east, west and south.
The Foreign Ministry would be allocated to the east, the ministries of economy, trade and justice to the west, and the defence, interior and finance portfolios to the south.
Dbeibah has also defended the "integrity" of the process leading to his election and demanded the publication of the report claiming corruption.
The report prepared by UN experts is to be submitted formally to the UN Security Council in mid-March.
Some MPs have asked for the vote of confidence to be delayed until the report is published.
After three hours of debate, parliament called for a new session on Tuesday to give Dbeibah a chance to respond to questions.