Lawmakers loyal to Maduro staged a walkout from the opening session of the new assembly. Newly sworn-in congressional president Henry Ramos Allup promised to promote an agenda of "constitutional and peaceful change" in a country still led by Chávez's successor, whom the opposition has threatened to remove from office by referendum within the next six months.
"Here and now, things will change", he said. Maduro dismissed accusations his government is attempting to subvert democracy in Venezuela.
The voting of the legislature's new leadership followed debate over whether to take the oath of 163 or 167 lawmakers following a Supreme Court ruling barring four elected representatives from taking their seats over allegations of fraud, depriving the opposition of a two-thirds majority.
"This National Assembly is not about revenge...it's not the Assembly of the opposition but the Assembly for solutions", Capriles urged this week.
In an unusual move, state TV was broadcasting interviews with the opposition lawmakers and political leaders, each one arriving like a rock star and setting off applause.
Since the late Hugo Chavez took power in 1999, this assembly had been entirely dominated by his followers.
Instead, from the public gallery, the wife of jailed opposition leader Leopoldo Lopez held up a sign reading "Amnesty Now", referring to what's likely to be the legislature's first order of business: a law freeing dozens of activists jailed during anti-government protests in 2014 that resulted in dozens of deaths.
The leadership vote underlined a perennial split within the opposition that has seen moderates and hard-liners exchange barbs since their coalition's landslide victory over the socialists in December 6 legislative elections.
Even without the two-thirds majority, the opposition should be able to pass most of the laws it wants, as the president has limited powers to veto legislation.
Three members of the right-wing MUD coalition and one from the socialist PSUV alliance from the state of Amazonas were suspended after a Supreme Court decision.
The MUD nevertheless insisted its legislators would all turn up to be sworn in on Tuesday.
Outgoing assembly president Diosdado Cabello, however, accused MUD of having "assassins pardoning themselves".
President Nicolas Maduro responded saying that Venezuela would "not accept imperialism".
The socialist president asked his top ministers to resign after the party suffered crushing losses in December 6 legislative elections.
But voters punished him for the state of the economy, in the toughest challenge yet to his authority.
Sen. Bob Menendez (D-NJ) wrote a letter to President Obama on Monday calling for tough talk, sanctions and worldwide oversight following the Venezuelan elections that have shifted the political landscape away from Chavismo.
With the world's biggest known oil reserves, Venezuela has been suffering from a fall in the price of the crude, which has led to a deep recession.
"In the coming hours we will activate a contingency plan for the adoption and revision [of measures] in the field of economy - on the construction of a productive economy in the national, regional and local scale", Maduro told the Venezuelan AVN news agency, according to Sputnik.
