The results have sparked huge protests
Independent monitors in Madagascar have published evidence of serious irregularities during the first round of the country's presidential elections last December.
They recommend that the second round of voting be postponed until the results can be investigated further.
The opposition candidate, Marc Ravalomanana, claims that it is such irregularities that forced the second round in the first place.
He says fraud in the December vote robbed him of an outright victory. Provisional figures only gave him a narrow lead over President Didier Ratsiraka, and the High Court ordered a second poll.
Over the last few weeks tens of thousands of protesters have taken to the streets, demanding the resignation of the incumbent leader.
Despite the protests, President Ratsikraka began campaigning on Saturday in Antananarivo with only a handful of supporters.
Tampering
Calling for the second round of elections to be postponed until a full investigation into the first has been completed, the consortium, a group of civic and church groups, produced evidence that it said asked too many questions to ignore.
The group, sponsored by the international community to provide observers to the ballot, only managed to independently monitor 75% of the voting.
They said their work had been deliberately hindered to stop them collecting polling station returns, and cited proof that forms had been tampered with and that data from official local documents had been inaccurately copied into the official results.
Elliot Ranratsaraf from the consortium said the electoral procedure was seriously flawed:
"There were failures in the administration organisation of those elections, failures establishing the lists of voters. We found differences in the results. None of our suggestions have been taken into account by the administration and by the High Court."
Strike
The mass protests and general strike were suspended over the weekend but the opposition presidential candidate, Mr Ravalomanana has urged all government administrative workers to strike on Monday.
Meanwhile President Ratsiraka launched his campaign for the second round of voting. He is determined it will go ahead.
Tension is rising across the country with reports of clashes between rival supporters, and a roadblock believed to be run by pro-Ratsiraka demonstrators cutting off the capital from the country's main port and source of fuel and supplies.