Mexico's leftist presidential hopeful rejected a court decision to uphold his rival's slim lead and urged his supporters not to recognize a government that will likely be led by the ruling party candidate.
The Federal Electoral Tribunal's partial recount reduced Felipe Calderon's 240,000-vote lead over Andres Manuel Lopez Obrador by slightly more than 4,000 votes.
The court stopped short of declaring a winner in the race, saying it must still take an official tally, and decide whether the entire election was legitimate. Both must be done by Sept. 6.
Lopez Obrador compared the decision to a political coup, arguing that the judges were representing the interests of Mexico's ruling elite. His party lacks the seats in Congress to block legislation, but he vowed he would either wage an ongoing resistance or create an "alternative" government, which his supporters have said could collect taxes and offer services to people neglected by the ruling party.
"We will never again allow an illegal and illegitimate government to be installed in our country," he told thousands of his supporters camped out in Mexico City's main Zocalo plaza.
Fox's spokesman, Ruben Aguilar, dismissed the idea of a shadow government.
"We think this is a symbolic, political act that has no validity in the affairs of state," Aguilar said.
Lopez Obrador has been Fox's most outspoken critic and has pledged to be an even bigger gadfly during Calderon's administration. He repeatedly has demonstrated that he can mobilize millions against the government, forcing the hand of those who oppose him.
Lopez Obrador has called a giant rally for Sept. 16, Mexico's Independence Day, in the Zocalo, the symbolic heart of the nation, which has been occupied for weeks by protest camps.
The former Mexico City mayor claims fraud was responsible for Calderon's lead, alleging that electoral officials have reverted to crooked practices common before Fox's victory ended 71 years of one-party rule.
Fox leaves office Dec. 1, limited by law to a single, six-year term.
Several of the electoral court judges defended their work in an open session Monday as dozens of protesters pressed against the courthouse gates, demanding that the election be given to Lopez Obrador.
"Tolerance, the ability to listen, has prevailed over everything else," chief justice Leonel Castillo said.
He said some court officials had worked 20-hour days to review huge stacks of evidence submitted by both leading parties.
The judges repeatedly said they annulled only the ballots where it wasn't clear which party the voter was supporting, saying each challenge had to be specific and backed up by evidence.
"You can't just say: 'Well, there were irregularities,"' Castillo said, an apparent jab at Lopez Obrador's strategy of filing a mountain of appeals and claiming the entire vote was tainted.
Lopez Obrador has said he would accept nothing less than a full recount, arguing it would reveal that he was the race's true winner. The judges rejected that plea on Aug. 5, saying it was unnecessary and even illegal.