RIO DE JANEIRO — Flávio Bolsonaro, the eldest son of President Jair Bolsonaro of Brazil, has been charged with graft and money laundering as part of an investigation into the theft of public funds.
State prosecutors in Rio de Janeiro announced the charges in a brief statement issued late Tuesday night. They did not release a charging document or provide a detailed summary of the case because it remains under seal as the investigation continues.
The case has undermined one of the main promises that propelled Mr. Bolsonaro to victory in 2018: that he was singularly equipped to root out the culture of malfeasance in Brazilian politics.
The charges against Flávio Bolsonaro stem from a series of suspicious financial transactions involving staff members at his former legislative office in the Rio de Janeiro State Assembly. Flávio Bolsonaro was elected to the senate in 2018, the same year his father won the presidency.
Investigators say that the president’s son ran a scheme known as rachadinha, in which elected officials pocket part of the salary of legislative aides who accept employment on the condition of kicking back part of their pay. The tactic is common in the lower rungs of politics in Brazil.
In a statement posted on Instagram on Wednesday, Flávio Bolsonaro, 39, said, “I have done nothing illegal.” He accused prosecutors of a series of procedural missteps and said that the charges stemmed from a “fishing expedition” into financial records.
Prosecutors on Tuesday said that they had also filed criminal charges against Fabrício Queiroz, a close family friend who served on Flávio Bolsonaro’s state legislative office. Mr. Queiroz came under investigation when investigators discovered a series of suspicious bank transfers, including a handful to the first lady, Michelle Bolsonaro.
The president and the first lady have not provided a clear explanation for the payments, which totaled more than $16,000. The president has reacted angrily to reporters who raised the issue, telling one in August that he was tempted to “smash your mouth in.”
Prosecutors said that 15 people other than Flávio Bolsonaro and Mr. Queiroz faced charges in the case, which they said was built on the transactions and other actions that began in 2007 and continued for more than a decade.
Flávio Bolsonaro has invoked a series of legal protections that elected officials in Brazil enjoy to keep the case from moving forward. That has created obstacles that prosecutors have so far managed to overcome.
Under Brazilian law, prosecutors must persuade a court to accept the charges in order for Flávio Bolsonaro and the other suspects to formally become criminal defendants.
The newspaper O Globo reported on Wednesday that prosecutors got a big break in the investigation this year when one of Flávio Bolsonaro’s former legislative aides made a sworn statement admitting her involvement in a kickback scheme.
The former aide, Luiza Sousa Paes, told investigators that she agreed to kick back 90 percent of her wages to Mr. Queiroz on the condition that she was an employee only on paper. O Globo said her admission of guilt marked the first time that a person involved in the scheme had told prosecutors how it worked and provided corroborating evidence, including bank records.
The case is testing the independence and strength of Brazil’s justice system, which just years ago drew global acclaim as prosecutors took down dozens of powerful business people and politicians as part of a sprawling corruption investigation that came to be known as Operation Car Wash.
But the careers of several of the protagonists of that crusade have stalled in recent years, and court rulings have deprived prosecutors of some of the investigative and procedural tactics that enabled it.
Under Mr. Bolsonaro’s watch, the executive branch and the courts have weakened anti-corruption measures. And the president himself is facing an investigation by the Supreme Court for obstruction of justice after his former justice minister accused Mr. Bolsonaro of seeking to replace a police chief in an effort to shield his family from criminal inquiries. Mr. Bolsonaro angrily denied the charges.