Senator Alessandro Vieira of Sergipe announced on Tuesday, September 15, 2026, that he will file a writ of mandamus with Brazil's Supreme Federal Court (STF) to force Senate President Davi Alcolumbre to install a congressional inquiry into Banco Master. The request has 41 signatures and has sat on the Senate leadership's desk for six months. According to the magazine VEJA, the filing was expected on Tuesday itself.
Vieira says he cannot get an answer from the Senate leadership. Alcolumbre, he says, has not responded to formal requests, official letters, rulings or phone calls on the matter. The 41 signatures exceed the constitutional minimum to open an inquiry, one third of the Senate's 81 members, or 27 names. A CPI, as congressional inquiries are known in Brazil, can compel testimony and demand documents with powers of a judicial authority.
"I will file a writ of mandamus, once again, asking the Supreme Court to order the president of the House to install a Parliamentary Commission of Inquiry specifically to investigate the ministers' relationship with Daniel Vorcaro," Vieira told Poder360.
What the inquiry would investigate
The inquiry would examine the ties between Justices Dias Toffoli and Alexandre de Moraes and Daniel Vorcaro, the founder of Banco Master. Vorcaro is under investigation for leading the largest fraud recorded in Brazil's financial system, Poder360 reports. In the filing, Vieira argues that the Senate cannot stay silent on suspicions involving members of the country's top court, and that the Constitution gives Congress the power to investigate members of the judiciary.
"This House cannot walk away from its responsibility. The Constitution is wise. It was not for nothing that the Constitution opened the possibility of prosecution for crimes of responsibility for us," Vieira said in a statement quoted by VEJA. "What we are defending is investigation. It is justice and law for everyone." He also linked the request to the report of the Senate's organized crime inquiry. "It is a deep infiltration of organized crime that reached the highest courts. I have said this since February 2019," he said, according to Poder360.
Pressure on the day of a Supreme Court session
The announcement came on the same day the full Supreme Court began reviewing a Federal Police report that cites Moraes's relationship with Vorcaro. It was the first time the court weighed opening an investigation into one of its own justices, G1 reports. Toffoli, one of the two justices the proposed inquiry targets, recused himself and did not vote. The session ended without a decision, suspended by a request for review from Justice Flávio Dino.
The next step is the filing of the writ at the STF, which will decide whether to order Alcolumbre to install the committee. In the plenary, Dino has up to 90 days to review; if he does not speak, the case automatically returns to the docket. Court President Edson Fachin must decide whether to keep a September 23 session on Justice André Mendonça.