Cesar Perez Vivas, an opposition politician, said the Venezuelan president wanted to "remain in power forever", and vowed to challenge any future constitutional changes that could let the president run for re-election in 2012.
Chavez was comfortably re-elected in national elections in 2006 and survived an opposition coup against him in 2002.
Meanwhile in Caracas, thousands of anti-Chavez protesters took to the streets to demonstrate on the anniversary of the toppling of General Marcos Perez Jimenez, Venezuela's last military ruler.
Protesters waved flags and chanted anti-Chavez slogans.
Police fired tear gas at some demonstrators but no casualties were reported.
Chavez supporters commemorated the day by laying wreaths at the grave of Fabricio Ojeda, a journalist who helped organise street protests that culminated in the end of Perez Jimenez's rule.