(Adds plenary to decide paper ballot issue)
By Anthony Boadle
BRASILIA, Aug 6 (Reuters) - Brazil's far-right President Jair Bolsonaro ignored calls to drop his feud with the Supreme Court on Friday and called one of its justices a "son of a whore," amid rising tensions over his unfounded claims the nation's voting system is vulnerable to fraud.
Speaking to supporters in southern Brazil, he insulted Luis Roberto Barroso, the top court justice who also heads the Supreme Electoral Court. The insult was uttered during a live broadcast shared on Bolsonaro's Facebook account but later deleted. Copies continue to be shared on social media.
Justice Barroso, speaking at a forum on electoral systems after the comments, said that if his actions were causing such a nuisance, it was a sign he was doing his job properly.
Bolsonaro has railed for weeks against the electronic urns used in Brazil and pushed for the adoption of printed receipts that can be counted if any election result is disputed.
Critics say Bolsonaro, like former U.S. President Donald Trump, is sowing doubts in case he loses next year's presidential election. He has threatened not to accept the result if the system is not changed.
With his popularity falling after overseeing the world's second-highest COVID-19 death toll, opinion polls show Bolsonaro trails former leftist President Luiz Inacio Lula da Silva, though neither of them has officially announced they will run.
Earlier this week the Supreme Court approved an investigation into the president's unfounded accusations about voter fraud.
On Thursday, in Bolsonaro's worst set-back in Congress since taking office in 2019, a lower house committee voted to shelve a constitutional amendment he has been pushing that would have adopted printed ballots.
Speaker Arthur Lira, however, said on Friday he would put the controversial amendment to the plenary despite the committee defeat. He explained the decision saying that a quick resolution was preferable because political tensions over the issue are holding up the country's legislative agenda.
The proposal is not expected to clear the lower chamber where constitutional amendments need three-fifths of the votes.
Earlier on Friday, Senate President Rodrigo Pacheco criticized Bolsonaro for his attacks on the Supreme Court and offered to mediate, saying the president's insults against Barroso were unacceptable.
Pacheco said Bolsonaro must respect the results of next year's election even if he fails to change the all-electronic voting system - which the president groundlessly claims is vulnerable to tampering.
"Any threat, however slight, to this democracy will be promptly rejected by the Senate," Pacheco said in a GloboNews television interview.
The Senate head said anyone advocating a "democratic retreat" or the suspension of next year's elections would be seen as an "enemy of the nation."
"I think a majority in Congress at this moment want to maintain the electronic voting system," he said. (Reporting by Eduardo Simoes and Anthony Boadle Editing by Mark Potter, Alistair Bell and Sandra Maler)
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