A supreme court judge has given Brazil’s ex-president, Jair Bolsonaro, 48 hours to explain police claims he was planning to flee to Argentina to avoid punishment for allegedly masterminding a failed coup after losing the 2022 election.

Bolsonaro’s trial for the alleged attempt to seize power is scheduled to conclude early next month. The far-right populist faces more than four decades in prison if found guilty.

Court documents made public on Wednesday night showed federal police investigators had found a draft asylum request on the ex-president’s mobile phone addressed to Argentina’s rightwing president, Javier Milei. In the undated and unsigned document, Bolsonaro claimed he was “facing imminent arrest”​ for political motives and needed “urgent” sanctuary overseas.

An Argentinian government source told the Reuters news agency that Milei’s office had not received a letter. But Brazilian police claimed the document indicated Bolsonaro had “planned to flee the country, in order to prevent the law being enforced”.

After the document was released as part of a 170-page police report, supreme court justice Alexandre de Moraes demanded answers from Bolsonaro’s lawyers. “The evidence gathered by the federal police indicate that Jair Messias Bolsonaro was in possession of a document designed to enable him to escape national territory,” Moraes wrote in his dispatch.

Bolsonaro, who was president from 2019 until the end of 2022, was placed under house arrest in early August after the supreme court decided he had violated a court order banning him from using social media. But Moraes’s 48-hour ultimatum reportedly fuelled fears among Bolsonaro supporters that their 70-year-old leader could be now taken into custody to stop him absconding before his final judgment, which is due to start on 2 September and conclude on 12 September.

Bolsonaro’s lawyer, Paulo da Cunha Bueno, admitted that the idea of going to Argentina had been suggested to his client but that Bolsonaro had rejected it. “Fleeing was never an option,” he told journalists.

Bolsonaro stands accused of plotting to overturn the result of the 2022 election, which he lost to his leftwing opponent Luiz Inácio Lula da Silva. He denies those charges, but political and legal experts – and many of Bolsonaro’s allies – are convinced he will be convicted.

The accusation that Bolsonaro had planned to flee Brazil for Argentina came as federal police formally accused the ex-president and his congressman son, Eduardo Bolsonaro, of trying to interfere in Bolsonaro’s judgment by encouraging US officials to put pressure on the supreme court. If found guilty of that offence they could receive a sentence of up to 12 years.

Eduardo Bolsonaro moved to the US in February and has spent recent months lobbying Donald Trump’s administration – with some success – to pile pressure on Brazil’s supreme court justices and Lula’s government over his father’s trial.

In July Trump slapped 50% tariffs on Brazilian imports in retaliation for what he called a “witch-hunt” against Bolsonaro and announced the imposition of sanctions on Moraes, who is presiding over Bolsonaro’s trial.

Eight of Brazil’s 11 supreme court judges, including Moraes, have been stripped of their US visas, as have the wife and 10-year-old daughter of one of Lula’s closest allies, the health minister, Alexandre Padilha.

“It’s really a political execution that they’re trying to do with Bolsonaro. I think that’s terrible,” Trump told reporters last week.

In other developments during a dramatic 24 hours for Brazilian politics, Silas Malafaia, a powerful and wealthy evangelical pastor who is one of Bolsonaro’s most vocal cheerleaders, was questioned by police after flying back from Portugal to Rio.

Malafaia, who is also being investigated by federal police over suspicions he too tried to influence the outcome of Bolsonaro’s trial, has now been banned from leaving the country and communicating with Bolsonaro and his son and has been ordered to surrender his passports. “You’ll have to arrest me to silence me,” Malafaia shouted at reporters after being released.

The federal police report also exposed the foul-mouthed infighting that appears to be playing out between members of the Bolsonaro clan and key supporters in the lead-up to the ex-president’s judgment.

In one WhatsApp exchange found on Jair Bolsonaro’s phone, which was seized as part of police investigations, Eduardo Bolsonaro reacts to an interview in which his father criticised him, writing in all capitals: “Go and fuck yourself you fucking ingrate!”

In another message, from Malafaia to Jair Bolsonaro, the firebrand church leader attacks Eduardo Bolsonaro for publicly celebrating Trump’s tariffs on Brazilian imports. “I’m sorry, president. This son of yours Eduardo is an inexperienced prick who is handing the nationalist discourse to Lula and the left … a complete idiot. I’m fuming!”

In a statement, Eduardo Bolsonaro criticised the police for “leaking private, absolutely normal conversations”. He called the move “shameful” and politically motivated and denied trying to interfere in his father’s trial.

Polls suggest Lula has received a boost after Trump’s attempts to pressure Brazil’s institutions, with more than 70% of Brazilians opposed to the US president’s actions and only 21% supporting them. A poll released on Thursday showed Lula beating all of his potential rightwing rivals in next year’s election, including Bolsonaro’s wife, Michelle Bolsonaro, Eduardo Bolsonaro, and a handful of conservative state governors battling to inherit leadership of Bolsonaro’s political movement.