He said he would prove that illicit money was used to buy votes and secure the victory of centrist candidate Enrique Pena Nieto, who denies this.

Mr Lopez Obrador wants the result of the vote to be deemed invalid.

Mr Pena Nieto was confirmed the winner on Friday after a final recount, with 38.21% to Mr Lopez Obrador's 31.59%.

'Sore loser'

Mr Lopez Obrador, from the Party of the Democratic Revolution (PRD), lodged the challenge to Mexico's Federal Electoral Institute (IFE) just hours before the midnight filing deadline.

"The purchase and manipulation of millions of votes cannot give certainty to any result nor to the overall electoral process," he told reporters.

Mr Lopez Obrador also said Mr Pena Nieto had broken campaign rules by overspending and that Mexico's media was biased in favour of the PRI candidate.

"Article 41 of the constitution, which states that elections must be free and fair, was violated," the left-wing Mr Lopez Obrador said.

In 2006, after losing the presidential election by a narrow margin, he led weeks of protests that caused disruption in central areas of Mexico City.

Pedro Joaquin Coldwell, the head of Mr Pena Nieto's Institutional Revolutionary Party (PRI), dismissed Mr Lopez Obrador's accusations as "baseless".

He also described the PRD candidate as a "sore loser".

Mr Lopez Obrador's accusations of irregularities led to a re-check of about 50% of votes after the 1 July poll's results were announced.

The electoral body then said that following the recount there was no reason not to accept the result.

The IFE will early next week submit the complaints and the evidence to the Federal Electoral Court. The court has until early September to address the complaints and rule on the validity of the election.