Maduro submitted the report in writing from Chavez's government while the president remained in Cuba undergoing treatment after his fourth cancer-related surgery. Opposition politicians argued that the annual speech should have been postponed because the president is supposed to deliver it, and about a dozen walked out in protest.
Maduro announced during the speech, a day after visiting with Chavez in Cuba, that the president designated former vice president Elias Jaua as the new foreign minister. Maduro had kept the foreign minister's post after his appointment as vice president in October.
Opposition leader Henrique Capriles said the naming of Jaua as foreign minister should be reviewed because it was unclear under what authority the vice president was acting when such powers belong to the president alone.
Only a portion of the opposition's representatives walked out of the National Assembly session.
Reflecting critics' charges of heavy Cuban influence in the political events unfolding in Venezuela, one of the legislators who left, Maria Corina Machado said: "The government of Venezuela today is in Cuba, and that's in violation of the constitution."
Oil Minister Rafael Ramirez dismissed the opposition's allegations that the government was acting illegally by going ahead with the special legislative session.
"There's no constitutional controversy," Ramirez told reporters, calling the politicians who walked out "the most extremist sector of the far right."
It was the second time in less than a week that Maduro has presided over an event that would normally have been led by Chavez. Maduro says Chavez remains in charge as president, though it remains unclear when the president might be well enough to address Venezuelans or return home.
"It's declared that they're governing in the name of someone about whom it isn't known for sure how he has been in the past month," said Edgard Gutierrez, a political analyst. "His name is repeated insistently in a huge propaganda operation and a sort of deification, but without it being known whether he will be able to govern again."
Re-elected in October, Chavez has not made any public comments since his latest cancer surgery Dec. 11.
He has been fighting an unspecified type of pelvic cancer, and his long silence has fed speculation about why he hasn't addressed the country by phone on television, as he did during past treatments in Cuba. Government officials have said Chavez is being treated for "respiratory deficiency."
Officials have indefinitely postponed Chavez's inauguration despite complaints by the opposition that the move was unconstitutional.
During last January's the state of the union address, Chavez spoke for nine hours before lawmakers even as he was undergoing cancer treatments.
This year, Maduro spoke for about 15 minutes and turned over to National Assembly President Diosdado Cabello two red books containing the government's annual report.
Maduro cited a clause in the constitution that says the vice president may present reports to the legislature if asked to do so by the president.
"Nicolas didn't come to take the place of the president. He came to bring the documents ... under instructions from the president," Cabello told reporters.
Dozens of Chavez supporters were allowed through the gates into the courtyard of the National Assembly. They cheered for pro-Chavez politicians and chanted: "With Chavez and Maduro, the nation is secure."
Earlier Tuesday, Maduro said Chavez has been making progress in his treatment for a severe respiratory infection and asked questions of his aides during a visit Monday.
Maduro said he and other officials provided Chavez with an update on "the government in a new stage" and other matters.
"He asked our friend Rafael Ramirez about (certain) aspects" of the government, Maduro said in a televised meeting with state governors.
"Our commander is climbing the hill, he's advancing, and that fills us with great happiness," he said.
Maduro made his comments about Chavez's health at a gathering of state governors in Caracas after returning from Cuba along with Ramirez, Cabello and Attorney General Cilia Flores.
Some government foes chafed at a weekend meeting in Havana between Chavez's inner circle and Cuban President Raul Castro. But Maduro, who is thought to have close ties to Cuba's government, dismissed concerns of any undue Cuban influence.
"There are those who say we're a colony of Cuba. It's really an offense against Cuba and against Venezuela," Maduro said.
Three opposition governors attended the meeting led by Maduro on Tuesday morning, including Capriles, who was defeated by Chavez in the presidential election in October. Capriles shook hands with Maduro in a brief exchange at the event.
During Chavez's five-week absence, some Venezuelans have begun speculating about whether his cancer could force him from office and require a new presidential election.
While many of Chavez's followers said they hope he will recover and return home, opposition lawmaker Carlos Ramos said Maduro's repeated appearances in the president's place suggest an effort to promote him as a candidate.
"What I hope is that they call elections soon," Ramos said.