Venezuelan Vice President Nicolas Maduro took the place of ailing President Hugo Chavez by delivering a short speech and turning in a state-of-the-nation report amid legal debate about his legitimacy.

Mr. 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.

Mr. Maduro announced during the speech, a day after visiting with Mr. Chavez in Cuba, that the president designated former vice president Elias Jaua as the new foreign minister. Mr. Maduro had kept the foreign minister’s post after his appointment as vice president in October.

Opposition leader Henrique Capriles said the naming of Mr. 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,” Mr. 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 Mr. Maduro has presided over an event that would normally have been led by Mr. Chavez.

Mr. Maduro says Mr. 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, Mr. Chavez has not made any public comments since his latest cancer surgery December 11.

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