Brazilian prosecutors have charged former president Jair Bolsonaro with allegedly orchestrating a far-right conspiracy to retain power through a military coup, which could lead to decades of imprisonment if he is convicted.

Attorney General Paulo Gonet filed charges late on February 18 against Bolsonaro and six close associates, accusing them of leading a criminal organisation with an "authoritarian power project", according to court documents.

The charges, which could result in a 38 to 43-year prison sentence, include attempted coup d'état and involvement in an armed criminal association.

They follow a federal police investigation that produced an 884-page report alleging Bolsonaro's central role in a plot to prevent President Luiz Inácio Lula da Silva from taking office.

"I'm not at all worried about these accusations," Bolsonaro told reporters.

The former president has consistently denied any wrongdoing.

The prosecution alleges the conspiracy included a scheme known as "Green and Yellow Dagger" to create political upheaval by targeting top officials.

"The plan was thought up and brought to the attention of the president of the republic [Bolsonaro], who agreed to it," the attorney general's 272-page report stated.

The charges come after Bolsonaro's supporters stormed government buildings in Brasilia on 8 January 2023, following his defeat in the 2022 presidential election. The event drew comparisons with the January 6, 2021 riot in Washington, where violent supporters of President Donald Trump stormed the US Capitol to disrupt Congress' certification of Joe Biden's victory, following Trump's false claims that the 2020 election was "stolen".

Last month, Brazil's Supreme Court barred Bolsonaro from leaving the country to attend Trump's inauguration, citing concerns that he might flee justice amid ongoing investigations into alleged coup plotting.

Prosecutors have also charged 33 other individuals, including several high-ranking military officials: former defence ministers Gen Walter Braga Netto and Gen Paulo Sérgio Nogueira de Oliveira, former spy chief Alexandre Ramagem, former justice minister Anderson Torres, former institutional security minister Gen Augusto Heleno, and former navy commander Adm Almir Garnier Santos.

Netto has denied involvement, while the others have not yet commented publicly.

The involvement of senior military figures marks an unprecedented development in Brazilian justice, according to Carlos Fico, a historian at Rio's federal university.

"The indictment of generals through a judicial process led by the federal police, with the endorsement of the country's attorney general and [that is] set to be judged by the supreme court, is unprecedented in Brazilian history," Fico said.

The president of Lula's Workers' Party, Gleisi Hoffmann, called the charges "a crucial step in the defence of democracy” and the rule of law.

Bolsonaro's senator son, Flávio Bolsonaro, rejected them, claiming there was "absolutely no proof against” his father.

The Supreme Court is expected to consider the case in the first half of this year. The charges represent one of the most significant legal challenges to a former Brazilian president in the country's democratic history.

Legal experts say the case could set important precedents for holding political leaders accountable for attacks on democratic institutions.

The prosecution marks a departure from Brazil's historical pattern of granting amnesty to military figures involved in anti-democratic actions, a practice that followed the country's 1964-1985 dictatorship.