Mexico's National Electoral Institute (INE) has denied former president Felipe Calderon's bid to register his Free Mexico movement as a new political party, saying some of its funding was questionable.
Calderon ruled Mexico from 2006-2012. He has been trying to convert the Freedom and Democratic Responsibility group that he runs with his wife, Margarita Zavala, into a political party to contest the 2021 mid-term congressional elections.
INE's general council rejected the party in a seven-to-four vote, saying late on Friday that its decision was due to Free Mexico "having more than 5% of contributions from unidentified people."
The decision can still be challenged before Mexico's Electoral Tribunal, however.
INE President Lorenzo Cordova said the institute had questions about the origin of 8.2% of the group's financing, which is why he voted against it.
Calderon's supporters called the decision a blow to democracy and Calderon, a vocal critic of President Andres Manuel Lopez Obrador, vowed to continue the political battle.
"They are not going to stop us," he tweeted after the decision. His wife, meanwhile, said they would "immediately challenge this absurd resolution."
The 2021 mid-term lower house elections are due to be held in the middle of next year and will decide whether Lopez Obrador's leftist Morena party will keep control of Congress.
INE's decision comes as Mexican activists have begun gathering signatures for a referendum on charging former presidents with graft, heeding calls by Lopez Obrador, who says he would respect the outcome of a public vote on the issue.