The five main opposition parties boycotted Sunday's election and barely 25% of the 14 million voters took part, election officials said.
But if confirmed, the results would give Chavez more than the two-thirds majority needed to change the constitution so that Chavez, a former paratroop colonel, can stand for a new term in power.
William Lara, who heads Chavez's Fifth Republic Movement (FRM), told reporters on Monday that the ruling coalition had won all 167 seats. He said the FRM will have 114 seats, with the rest also going to parties that support Chavez.
Lara said that after 5 January, when the new legislature is inaugurated, Venezuela will still have a "multi-party national assembly, which will include various civic groups and independent deputies".
Opponents of President Chavez
have so far failed to unseat him
Jorge Rodriguez, president of the National Electoral Council (NEC), said the low turnout was due to "torrential rains that have prevented voters from getting to polling places".
But opposition parties that withdrew from the election said the low turnout undermined the legitimacy of the result.
Among those that withdrew were the Democratic Action Party and COPEI, which for decades alternated in power.
Henry Ramos Allup, who leads Democratic Action, said that the new legislature was legal, but "it is not legitimate because it is a body in which the whole Venezuelan population is not represented".
Opposition forces complained that the electronic voting machines used can record fingerprints, allowing authorities to know how a person voted, though election officials agreed to switch the feature off. They also said that the electoral council was stacked with Chavez supporters.
The NEC chief said that "the voting went ahead with absolute normality". Hundreds of election monitors from the European Union and the Organisation of American States also declared the vote legitimate.
But the opposition group Sumate alleged widespread irregularities. "We have received complaints from all parts of the country," said Alejandro Plaz, a spokesman for the organisation.
Julio Borges, a prominent opposition member, said: "Venezuela is speaking with its silence."
Venezuela's opposition has failed in repeated attempts to oust Chavez, a left-winger and an ally of Fidel Castro, Cuba's leader.
"The old parties are already dead but are refusing to die"
"The old parties are already dead but are refusing to die," Chavez said on Sunday after casting his ballot in Caracas.
Chavez earlier accused the opposition of seeking to lead Venezuela "down a violent path", and called its boycott part of a "subversive" US-inspired plot aimed at denying him a new six-year term in the December 2006 presidential election.
There were some reports of violence during the vote. A senior military official said an oil pipeline was set ablaze at two points.
Chavez led a coup attempt in 1992, was elected president in 1998, re-elected in 2000, survived a coup in 2002 and fought a recall referendum in 2004. Huge spending on welfare and health, funded by Venezuela's oil wealth, has sustained his strong support among many Venezuelans.