By Lisandra Paraguassu and Maria Carolina Marcello
BRASILIA (Reuters) -Opposition parties on Friday filed constitutional complaints at Brazil's Supreme Court against a pardon granted by far-right President Jair Bolsonaro to an ally who the court sentenced to nearly nine years in prison for anti-democratic threats.
On Thursday, Bolsonaro decreed a pardon for Congressman Daniel Silveira, a former Rio de Janeiro police officer, a day after the court sentenced him to 8 years and 9 months in prison for interference with the free exercise of government and threatening judicial authorities.
The pardon has exacerbated tensions between the nation's executive and judiciary, threatening a constitutional crisis during an election year when Bolsonaro is seeking a second term.
Silveira provoked controversy last year by questioning the integrity of several justices on the top court, known as the STF, and calling on Bolsonaro supporters to invade its building.
He said an anti-democratic decree in place during Brazil's 1964-1985 military dictatorship should be reinstated.
The Sustainability Network party, or Rede Sustentabilidade, argued that the presidential pardon breached the constitution because it served Bolsonaro's personal interest in protecting an ally and not the public interest.
The president cannot take "unconstitutional measures" just to please his voters, or else Brazil was at risk of becoming once again a "tyrannical state" subject to the will of an authoritarian ruler, the party said.
The left-wing Democratic Labor Party and Socialism and Liberty Party filed similar actions. A source at the court said some justices believe the pardon can be opposed, but others prefer to avoid a new confrontation with the president.
Bolsonaro and his allies have complained of increasing judicial overreach by the STF. They criticized the Wednesday ruling as a politically motivated threat to free speech.
His opponents cheered the verdict because they see the former army captain and his cohorts as a threat to democracy, and some fear Bolsonaro may not concede defeat if he loses in October since he has argued that Brazil's electronic voting system is vulnerable to fraud.
Former Chief Justice Carlos Ayres Britto said the Constitution does not allow pardoning attacks on democracy.
Lawyer Belisario dos Santos Junior said Brazil's Constitution does give presidents the prerogative to pardon individuals even though they may be highly controversial, and noted the 1974 pardoning of Nixon by U.S. President Gerald Ford.
But he said Bolsonaro abused his power pardoning a person who offends democracy and the Supreme Court the way he has done.
(Reporting by Lisandra Paraguassu, Maria Carolina Marcello and Ricardo Brito; Writing by Peter Frontini and Alistair Bell)