By Andrew Cawthorne

CARACAS (Reuters) - Venezuela President Nicolas Maduro's socialist government sought on Tuesday to scupper a push by the opposition to oust him this year via a referendum, while his opponents called for protests.

As the OPEC nation faces an unprecedented economic crisis, both sides are deadlocked over a provision in the constitution allowing a recall referendum halfway through the president's six-year term.

Government supporters lodged a complaint at the election board saying the Democratic Unity (MUD) coalition falsified signatures in an initial collection to trigger the process.

"They are committing grave fraud and corruption," senior Socialist Party leader Jorge Rodriguez told reporters outside the election council, saying signatures of nearly 11,000 dead people and 3,000 minors were included.

Maduro, 53, who won election to replace Hugo Chavez in 2013, has vowed there will be no referendum, and the election council has been dragging its feet over the process.

The opposition urged supporters to march to the council's Caracas headquarters on Wednesday to demand it validate the first round of signatures, 1 percent of registered voters in each state. Previous protests this year have turned violent.

"We are in an emergency," opposition leader Henrique Capriles said in a speech at a public event. "All the prices are rising and the government does nothing. ... To change this situation, there has to be political change."

If the referendum process proceeds, the next stage would be for the opposition to obtain 20 percent, or nearly 4 million signatures, asking for the vote.

In a communique, the election board said it would assess the validity of the first round of signatures on Monday, adding it was worried about aggression against its staff by protesters.

In addition to Tuesday's action, the government has lodged a plethora of court challenges. It also says there is not enough time to organize a referendum this year because the opposition waited too long before activating the mechanism.

The timing is important because if Maduro loses a referendum this year, there would be a new presidential vote - which polls indicate he would likely lose.

If Maduro loses a referendum after January, he would be replaced by his vice president, leaving the Socialist Party in power until the next presidential election scheduled for the end of 2018.

Critics blame failed socialist policies for Venezuela's 2-1/2 year recession, the world's highest inflation, product shortages and long lines at shops. Maduro says the fault lies with falling oil prices and an "economic" war by opponents.

(Additional reporting by Diego Ore; Editing by Eyanir Chinea and Richard Chang)