Liviu Dragnea, the deputy chairman of the opposition Social Democrats party, said on Tuesday that the party has received reports from all of Romania's 41 counties of bribery, multiple voting and possibly forged ballots sent to central election authorities.
"We have truckloads of evidence, they are coming in waves," he said. Dragnea said the party knew of 13,000 cases of multiple voting.
He also claimed that on Monday senior members of the Democratic Liberal Party, which supports Basescu, had ordered local government officials around Romania to erase video surveillance from polling stations.
Caretaker Prime Minister Emil Boc dismissed the allegations and accused the Social Democrats of not knowing how to accept defeat.
Dragnea said the party would officially contest the result of Sunday's vote to the Constitutional Court later Tuesday. The court would make a ruling, likely in the coming days, and Basescu could not take office until the ruling had been made.