The National Electoral Board (CNE) is due to decide whether to accept or reject an initial petition with 1.8 million signatures endorsing a recall vote against Maduro, whom the opposition accuses of driving Venezuela into economic and political chaos.
Maduro's opponents warn that the country faces an explosion of unrest if authorities do not allow a recall referendum this year.
Enrique Marquez, the deputy speaker of the opposition-controlled legislature, said yesterday the referendum was the only "escape valve" for a country racked by economic collapse, hyperinflation, shortages of food and medicine, daily power outages and violent crime.
The opposition accuses the CNE of dragging its feet to protect Maduro, the political heir to the late leftist firebrand Hugo Chavez.
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Maduro's camp, for its part, accuses the opposition of massive fraud in its petition drive.
Even if the CNE accepts the petition submitted on May 2, Maduro's opponents face a long and winding road to call a referendum.
And they may not get there by the crucial date of January 10 -- four years into the leftist leader's six-year term -- when a successful recall vote would trigger new elections rather than simply pass power to Maduro's vice president.
If that happens, signatories must then present themselves in person to confirm their identity with a fingerprint scan.
The opposition must then submit a second petition, this time with four million signatures, or 20 per cent of the electorate, for the CNE to organize a referendum.
The pro-recall camp would need more votes than Maduro won the 2013 election with -- some 7.5 million -- to remove him from office.