Moldova's liberal opposition parties declared they would lodge an appeal against the recount in the country's highest court, claiming voting lists were swollen with 400,000 extra people who were either dead or living abroad.
Nicolae Railean, the head of the Our Moldova Alliance, which won 11 parliamentary seats, said: "We will appeal the results of the recount. We see here the same fraud as during the first vote count.
"We know that electoral lists were falsified and ghost voters were counted. We will present our evidence to the courts."
International observers, including the Organisation for Security and Co-operation in Europe (OSCE), Europe's election watchdog, gave their overall approval to the original voting process.
The Constitutional Court, which must confirm the recount, is to sit on Wednesday, but could take several days examining opposition complaints before issuing a ruling.
The recount was initiated by Voronin after the announcement of the first set of results prompted demonstrations on April 7 in Chisinau, the capital, attended by up to 30,000 people.
The protests led to more than 200 arrests and dozens of injuries, as well as the death in custody of one demonstrator.
Voronin said the violence, in which some demonstrators ransacked his office and parliament, were part of a plot to seize power and were fomented by Romania, which shares a cultural and linguistic heritage with Moldova.
Romania denies the charges.
Voronin, in power since 2001, cannot run for a third term, but says he wants to keep a decision-making role.
His office also said Mirek Topolanek, the Czech prime minister, whose country holds the rotating European Union presidency, would shortly be visiting the country to hold talks on the post-election events.
Moldova, which lies between Ukraine and Romania, is officially Europe's poorest country.