Mexico’s president Andrés Manuel López Obrador is being accused of using his public war on corruption to force out opponents while turning a blind eye to questionable behaviour by allies.

“There’s a very big contradiction between what the president promised and what is happening. There is a politicisation of justice,” said María Amparo Casar, executive president of Mexicans Against Corruption and Impunity, an NGO.

The latest incident came last month, when Eduardo Medina Mora, a former attorney-general and security minister, quit as a Supreme Court judge. Mr López Obrador said Mr Medina Mora had resigned to focus on an investigation into allegedly suspicious financial transactions.

Months earlier, the judge had denied allegations he had transferred large sums of money to international bank accounts in his name that were allegedly out of line with his income.

But when it later emerged that his bank accounts had been frozen just before he quit, and were unfrozen immediately afterwards, the government faced claims that it was manipulating the inquiry to oust a political opponent. Mr Medina Mora, who was named to the court by the president’s predecessor, Enrique Peña Nieto, from the long dominant PRI party, and served as minister under the rightwing PAN, denies wrongdoing.

Mr Medina Mora’s fate was seen to be in contrast to the treatment of Manuel Bartlett, head of the state electricity company CFE and a top ally of the president. He faced just an administrative probe after a media investigation uncovered a string of properties and companies linked to him and his family that he had omitted from his official income declaration.

Mr López Obrador has dismissed the media allegations against Mr Bartlett, who has denied wrongdoing, as “an attempt to besmirch the new government”. The CFE chief said properties and firms linked to Julia Abdala, his partner of more than 20 years, were not relevant to his declaration because “I have no wife or concubine”.

Mr Medina Mora and Mr Bartlett are not the only public figures to face scrutiny.

Carlos Romero Deschamps quit in October after almost three decades as powerful union boss at Pemex, Mexico’s state oil company, after being put under investigation for alleged corruption. The probe comes as Mr López Obrador says he is seeking to make Mexican unions more transparent and accountable. Mr Romero Deschamps denies the allegations.

By contrast, there has been no investigation into Yeidckol Polevnsky, head of the ruling Morena party, over a hefty tax waiver she was granted, and which she said resulted from an error by her accountant.

In another case, a judge who had upheld legal challenges against Mr López Obrador’s planned new Mexico City airport project — which is designed to replace a partially built $13bn hub which the president has scrapped — was placed under investigation for alleged corruption and suspended from his post for six months.

Within days, and with the judge, Jorge Camero, out of the picture, the remaining injunctions were denied, allowing the government to proceed with the project.

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“There is a double standard — behaving in a certain way against your opponents and a very different way against your allies,” said Marco Fernández at the Tec de Monterrey university.

Mexico has long been dogged by graft allegations. Edna Jaime, head of México Evalúa, a think-tank, said the country was now witnessing “a settling of scores” on the part of the government as it demonstrates its power.

It was widespread public disgust with spiralling graft that won Mr López Obrador last year’s election. He says he has delivered on his number one priority by refusing to tolerate government corruption and making graft offences serious crimes that carry automatic pre-trial detention. Opponents say his success to date is hard to measure.

Mr López Obrador’s allies counter that the first year of his administration has been devoted to putting the legal framework in place to root out graft, which Alejandro Armenta, a senator from Morena, estimated was equivalent to a sixth of the national budget. “The results are positive,” he said.

Graciela Márquez, economy secretary, went further, telling a recent conference that she gave Mr López Obrador 10 out of 10 for his progress and “corruption in the federal government has been eradicated” — an assertion that prompted a ripple of incredulous laughter from the audience.

Mr López Obrador has denied suggestions that his government is seeking to silence critics. “We want everyone to be able to express themselves, for the right to dissent to be guaranteed, that is what we are seeking,” he said last week.

But some analysts said the government’s actions suggest otherwise. “The political narrative is that corruption is over and so we shouldn’t be talking about it,” said Manuel Molano, head of think-tank the Mexican Institute for Competitiveness.

“What we are seeing . . . is perhaps the antechamber of a much more authoritarian regime than any we have seen in the last 40 years in Mexico.”

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