President Nicolas Maduro's closest challenger in this month's presidential polls, Henri Falcon, on Wednesday filed an appeal with the country's highest court to have the vote annulled.
Maduro was re-elected for a second six-year term with 68 percent of the vote in a poll boycotted by the main opposition and derided as a sham by the US, EU and 13 other Latin American countries.
"Today we are presenting before the Supreme Court of Justice the proper foundation of our case which demonstrates that such an electoral process is invalid," Falcon told journalists.
"The scope of this challenge must be the call for new elections in Venezuela," he told the court, adding that the May 20 ballot "did not exist and must be declared null and void."
Falcon, an ex-army officer, scored 21 percent of the ballot, from which more than half the electorate abstained.
Among Falcon's arguments is that Maduro offered cash incentives to many voters who could be tracked electronically through cards giving them access to government food aid programs.
"Bribery is punished," said Falcon. "It is punishable by law and you cannot appeal to the social policy of a state to buy votes."
He also denounced the use of state media to promote Maduro's campaign, and claimed "pressure and coercion" was used against opposition monitors in polling stations.
Falcon said polling stations in several areas remained open beyond their official closing time to allow more socialist party voters to cast ballots.
Venezuelan presidential candidate Henri Falcon shows his ballot on election day, during the vote which the main opposition boycotted