Brazilian President Luiz Inácio Lula da Silva vetoed legislation on January 8 that would have substantially shortened the prison term of his predecessor Jair Bolsonaro, who was convicted of coup plotting last year.

The veto came during a ceremony marking the third anniversary of anti-democratic riots in the capital, when thousands of Bolsonaro supporters stormed government buildings on January 8 2023, demanding the military overthrow Lula's newly inaugurated government.

Lula signed the veto at a federal government event defending democracy, rejecting the bill that Congress had approved in December. The legislation would have reduced Bolsonaro's 27-year sentence to approximately 20 years and shortened his time in closed regime imprisonment to about two years.

"January 8th is marked in history as the day of victory for our democracy. Victory over those who tried to seize power by force, disregarding the popular will expressed at the ballot box," Lula said at the presidential palace, one of the buildings targeted by rioters three years ago.

"Perhaps the most compelling proof of the strength of Brazilian democracy is the trial of the coup plotters by the Supreme Federal Court," he added.

Bolsonaro, 70, was imprisoned in November following his conviction in a landmark coup trial. Prosecutors said the scheme included plans to assassinate Lula, Vice President Geraldo Alckmin and Supreme Court Justice Alexandre de Moraes, but failed due to insufficient military support.

The former far-right president has denied the charges. His supporters, including US President Donald Trump, have denounced the prosecution as a politically motivated "witch hunt."

Congress retains authority to override the presidential veto. Senate President Davi Alcolumbre would need to convene a joint session for lawmakers to vote on whether to uphold or reject Lula's decision.

But Lindbergh Farias, the Workers' Party leader in the Chamber of Deputies, expressed confidence that the veto would be maintained. He noted the government would have more than a month to secure the necessary votes, requiring 34 lawmakers to change their positions from the original vote.

The legislation would have also benefited others convicted in the coup plot and more than 100 people imprisoned for participating in the January 2023 riots. The violence echoed the 2021 US Capitol attack by Trump supporters, as far-right demonstrators ransacked Congress, the Supreme Court and the presidential palace one week after Lula's inauguration for a third term.

Neither Alcolumbre nor Chamber President Hugo Motta attended the January 8 ceremony. According to Estadao, Alcolumbre's office said he remained on holiday in Amapá, whilst sources close to Motta indicated he viewed the event as overly partisan and polarising.

Meanwhile, Bolsonaro returned to hospital on January 7 for medical checks following a fall in prison. He received medical clearance after the examination. The former army captain, who suffered serious health complications from a 2018 stabbing during his campaign, spent a week hospitalised in December for groin hernia surgery and treatment for recurring hiccups.

As per current sentencing rules, Bolsonaro must remain imprisoned for a minimum of eight years. His lawyers' appeals for house arrest on health grounds have been unsuccessful.