Venezuelan opposition lawmakers warned democracy was under siege as they cleared out their offices for President Hugo Chavez's allies, who will take full control of the legislature January 5th.
Opposition deputies held 79 seats in Venezuela's outgoing National Assembly, while pro-Chavez lawmakers controlled 86 seats.
But an opposition boycott of December 4th elections allowed allies of the left-wing president to claim all 167 seats in the new Congress.
"Today the democratic parliament has died. Now they'll have a new, illegitimate, single-color parliament," Cesar Perez Vivas, secretary general of the COPEI party, said after the last ordinary congressional session for the year.
President Chavez has poured billions in oil revenues into projects for the poor in the world's fifth biggest crude exporting nation as part of his self-proclaimed socialist revolution, which he presents as an alternative to US policies in the region.
US officials and local critics say President Chavez has become an authoritarian menace at home by exerting political control over institutions like the courts and the electoral authority.
Most opposition parties abandoned the congressional elections days before the poll after accusing election officials of favouring President Chavez and saying they could not trust the voting system to guarantee a fair ballot.
The government rejected the boycott as sabotage orchestrated by Washington and suggested the parties involved should be outlawed. It said the discredited opposition dropped out when they realised they would be defeated.
Henry Ramos, secretary general of the biggest opposition group, Democratic Action, said during his final speech that his party would boycott next year's presidential elections, unless the government substituted the electoral authority.
"When there are no other candidates, will the government be able to convince the world that it has a perfect democratic model?" Mr Ramos asked. "We are leaving without nostalgic feelings, simply with concern that the national legislative power may be lost for good in Venezuela."
Opposition lawmakers said they were still hoping for a dialogue with the government on a new National Electoral Council that would replace what they say is a Chavez-controlled body that lacks voters' confidence.
Voter abstention in the December 4th election reached 75 per cent. European Union observers said the vote was clean, but urged Venezuela's parliament to name a new electoral council.
President Chavez has accused Washington of manipulating observers. "We'll see in January what kind of attitude they show," Gerardo Blyde, a deputy with Justice First party said. "Our actions will depend on that."