Brazilian president Michel Temer has told the nation that an incriminating audio recording of him had been doctored as he fought to save his job.
"That clandestine recording was manipulated and doctored with (bad) intentions," Mr Temer said at a news conference in the capital, Brasilia.
Mr Temer said he had filed a petition with the Supreme Federal Tribunal, the country's highest court, to suspend the corruption investigation into him until experts can analyse the audio that appears to show him endorse the payment of bribes to ex-House speaker Eduardo Cunha for his silence.
It is unlikely the court would do that, as it authorised the opening of the investigation into Mr Temer in the first place and ordered it made public.
Mr Temer noted the Folha de S. Paulo newspaper reported that the 39-minute recording had been edited.
The audio was first reported by Globo newspaper on Wednesday.
Mr Temer also questioned the motives of the man who made the recording, JBS meatpacking company executive Joesley Batista.
He accused Mr Batista of buying "large quantities of dollars to cause chaos on the exchange market" before giving the tape to prosecutors.
Mr Temer's claims about the audio and Mr Batista could not be immediately verified.
In the audio, Mr Temer apparently endorses bribes for Cunha, who is serving a 15-year prison sentence of corruption and money laundering and who led the impeachment push against President Dilma Rousseff last year.
Ms Rousseff was eventually ousted for illegally managing the federal budget, bringing Mr Temer, who was her vice president, to power.
Mr Temer's remarks were unlikely to have much impact on the spreading movement for him to resign.
Even if the audio was edited, Mr Temer's words to Mr Batista to keep up the payments to Cunha seem clear.
And Mr Temer did not mention the long list of other allegations against him, nor acknowledge that allies have started to bolt.
Soon before Mr Temer spoke, the Brazilian Socialist Party announced it was breaking from his coalition.
The loss of its seven senators and 35 deputies mean Temer's ambitious plans to reform the country's pension system and labor laws are even less likely.
The leaders of several other parties in Mr Temer's coalition also planned to consult with their members Saturday in Brasilia.
Brazil's highest court released documents on Friday revealing that the nation's top prosecutor is accusing Mr Temer of corruption, obstruction of justice and being part of a criminal organisation.
In one plea bargain released as part of the tribunal's document dump, Mr Temer is accused of taking $1.5m in bribes.
In another, Mr Temer is accused of pocketing about 350,000 US dollars of 4.5 million dollars in illegal campaign finance channelled by the Workers' Party for the 2014 presidential ticket that included Mr Temer as vice presidential candidate.
The calls for Mr Temer to resign have been joined by Globo, the flagship paper of Brazil's biggest media company, which had been supporting the president's legislative programme to boost an economy mired in its worst recession in decades.
The company generally wields enormous influence among Brazilians because of its popular soap operas and media dominance.
"The president has lost the moral, ethical, political and administrative conditions to continue governing Brazil," O Globo said in an editorial.
Attorney General Rodrigo Janot's formal presentation of evidence was an extraordinary development in a corruption probe that is upending politics and just about everything else in Latin America's largest nation.
Mr Janot accused Mr Temer and Senator Aecio Neves of trying to derail the three-year-old car wash investigation into a huge kickback scheme at the state-run oil company Petrobras via legislative means and by influencing police investigators.
Because the case involves a sitting president, the process is different than in any other kind of criminal case.
With a formal investigation now opened, Mr Janot will now decide whether his case is strong enough to send it for consideration by the Chamber of Deputies in Congress.
If at least two-thirds of the members of the lower house voted in favour, the case would be sent back to the top court, which would then decide whether to put Mr Temer on trial.
If the court decided to try Mr Temer, he would be suspended from office for up to 180 days. A conviction would permanently remove him from office.
At least eight pieces of proposed legislation to impeach Mr Temer have been submitted in Congress.