(Adds worker quote, opposition plans)
By Alexandra Ulmer
CARACAS, July 7 (Reuters) - Venezuela's President Nicolas Maduro has said all state workers must take part in a vote on July 30 for candidates to his controversial new superbody assembly, seeking to avoid an embarrassingly low turnout in a country seething with discontent.
Maduro has called for the Constituent Assembly, with powers to reform the constitution and supersede other institutions, in what he has said is an attempt to bring peace after three months of anti-government protests in which at least 90 people have died.
Opponents have said the leftist president is trying to formalize a dictatorship in the South American OPEC nation through what they view as a sham poll. They are planning a rival, unofficial referendum on July 16 to give Venezuelans a say on his plan.
Maduro has been trying to drum up his base, which mostly encompasses state workers and poorer Venezuelans.
"If there are 15,000 workers, all 15,000 workers must vote without any excuses," he told red-shirted supporters in the jungle and savannah state of Bolivar on Thursday night.
"Company by company, ministry by ministry, governorship by governorship, city hall by city hall, we're all going to vote for the Constituent Assembly. Do you understand? Do you agree," he said to a chorus of "Yes!".
Venezuela's roughly 2.8 million state employees, a sizeable part of the population of around 30 million, are often obliged to attend government rallies, and some have said they have already come under pressure to vote on July 30.
"This is crazy. (They're saying), workers who don't go to vote will be sacked," said one employee of state oil company Petroleos de Venezuela S.A., asking to remain anonymous because he is not authorized to speak to media.
"I'll vote, but null. I'm not going to vote for any of these nuts running for the assembly," he added.
A second PDVSA worker said company auditoriums were being used to give presentations about the constituent assembly.
"I'm worried ... but I'm committed to the cause and I won't vote," he said.
Many familiar faces of the ruling Socialist Party are vying for a seat, including former Foreign Minister Delcy Rodriguez and powerful party No. 2 Diosdado Cabello. Maduro's wife and son are also running.
The opposition has said Maduro's pressure on workers is another sign he is violating democracy. Opponents are calling on him to agree to elections to replace him amid a brutal economic recession that has Venezuelans unable to afford basic food and medicine.
According to a recent survey by pollster Datanalisis, seven in 10 Venezuelans are opposed to rewriting the constitution, which was reformed by late leader Hugo Chavez in 1999.
The Roman Catholic church has also come out against the plan.
"This congress has been pushed forward by force and its result will be to render constitutional a military, socialist, Marxist and communist dictatorship," Archbishop Diego Padron, who heads the main church authority Venezuela's Episcopal Conference, said on Friday.
The opposition coalition is hoping to further delegitimize Maduro's plans with their own vote, which will ask Venezuelans their views on rewriting the constitution, the opposition's alternative push for an election, and the military's responsibility for "recovering constitutional order."
Voting for the referendum will take place in some 1,766 sites and Venezuelans abroad, many of whom have fled Venezuela's meltdown, can participate, opposition lawmakers announced on Friday. University deans will oversee the process.
"This is a civic rebellion," lawmaker Freddy Guevara said during the press conference. "We're at a historic moment, I'm sure there will be a before and after July 16." (Additional reporting by Andreina Aponte, Eyanir Chinea, Diego Ore and Deisy Buitrago; writing by Alexandra Ulmer; editing by Andrew Cawthorne, Frances Kerry and Diane Craft)