Brazil's top prosecutor has charged former presidents Luis Inacio Lula da Silva and Dilma Rousseff with forming a criminal organisation, the latest accusations in Brazil's sprawling corruption scandal.

The prosecutor, Rodrigo Janot, alleged that eight members of the Workers Party, including Mr Lula and Ms Rousseff, committed a series of crimes involving state-owned oil firm Petrobras such as cartel formation, corruption and money laundering.

Brazil's Attorney General Rodrigo Janot

They were the first criminal charges to be leveled against Ms Rousseff, who was impeached in 2016 for breaking budgetary laws.

The 230-page document filed with the Supreme Court accused Mr Lula of heading the organization.

Mr Lula's lawyer said the law was being misused to persecute the former president.

The Workers Party said in a statement that the charges were baseless and being used to divert attention from other investigations, including one into a former federal prosecutor.

A representative for Ms Rousseff said the prosecutor's office had offered no evidence of the crimes and called on the Supreme Court to guarantee the right to defend against them.

Mr Lula, who is still Brazil's most popular politician, is appealing a corruption conviction that would bar him from running for president in 2018. He faces four other corruption trials.

The charges stem from the Operation Car Wash investigation that uncovered a cartel of companies paying bribes to officials to secure Petrobras contracts, revelations that have spawned a host of investigations that have shaken Brazil's political system and economy.