By Daniel Kai and Girish Gupta

CARACAS (Reuters) - Venezuela's opposition called on Monday for mass rallies nationwide on Oct. 12 to push for a referendum to recall President Nicolas Maduro this year as they seek to oust his Socialist Party in an early presidential election.

The campaign for a recall vote has run into resistance from the country's elections board, which is imposing further restrictions and argues it will take until 2017 to put the proper conditions for such a referendum in place.

The Democratic Unity coalition urged daily protests against "anti-constitutional" conditions set by the electoral board.

"We will overflow the streets peacefully all over the country so that the regime and its electoral agents know that the referendum ... will take place this year," Jesus Torrealba, head of the opposition coalition, told hundreds of supporters in Caracas on Monday.

Maduro's term in office runs until 2019. But if Maduro lost a recall this year, as polls suggest he would given the country's severe economic crisis, presidential elections would be called under the Constitution. If next year, the vice president would take over and serve out his remaining two years.

Venezuela's electoral council last week said the soonest a referendum could be held, if at all, would be early 2017. That would effectively guarantee that the Socialist Party remains in power until 2019, even as food shortages and soaring prices have many Venezuelans skipping meals.

The elections board has stipulated that 20 percent of voters in each of the country's 23 states must sign a petition Oct. 26-28 supporting a referendum for it to go ahead.

The opposition argues the 20 percent threshold needs only to be met nationally, representing about 4 million signatures, and says the electoral council is just a puppet of an increasingly authoritarian government.

The ruling Socialist Party, which has for months insisted that there will be no recall referendum held this year, dismissed the opposition's planned mobilization as part of a plot to destabilize the government.

Venezuelan officials blame the opposition for the timing, saying the coalition took three months to reach a consensus on the referendum and that fraud was committed in a preliminary signature drive.

"Those announcements that were made today are nothing more than a call to violence," said Socialist Party director Jorge Rodriguez, who in a press conference insisted the recall push was carried out through a fraudulent signature collection.

The opposition spent the weekend debating strategy before Monday's announcement at which Torrealba was flanked by opposition leaders in a show of unity by the historically divided bloc.

"The recall referendum has to be in 2016, the country's conditions demand it," said opposition supporter Joaquin Mendoza, a 68-year-old publicist.

"Otherwise there will be more dead in the street, more hunger," he added, in a reference to Venezuela's high murder rate.

(Reporting by Daniel Kai; Writing by Alexandra Ulmer; editing by Girish Gupta, G Crosse and Cynthia Osterman)