The federal judge presiding over the corruption-kickback investigation at Brazil's state oil company Petrobras urged senators on Thursday to oppose legislation that would allow judges and prosecutors to be charged with abuse of authority.

Judge Sergio Mors aid such legislation would be interpreted as an attempt to repress the "Operation Car Wash" investigation, which already has implicated lawmakers and business executives.

Moro spoke during a Senate debate one day after congress' lower house, the Chamber of Deputies, approved the measure that would permit defendants to sue authorities for alleged offenses against the "honor and dignity" of their offices. Prosecutors investigating the kickback scheme have threatened to quit if President Michel Temer signs the bill.

Moro said the bill was an attempt to intimidate prosecutors as they are nearing completion of plea agreement negotiations with construction company Odebrecht, which is at the center of the Petrobras case. The agreement is expected to implicate as many as 200 politicians suspected of receiving bribes in recent years.

"Perhaps this is not the best moment to legislate on abuse of authority considering the important investigations currently underway," Moro told the senators.

He said congressmen tried to prevent wider debate on the issue by approving the bill in a marathon session that began Tuesday night and ended early Wednesday.

Senate President Renan Calheiros, who was sitting next to Moro, denied the bill was drawn up to intimidate prosecutors investigating the Petrobras scheme.

"Operation Car Wash is sacred for it reduces the impunity that reigns in our country," he said.

Hours later, the Supreme Court said it would open legal proceedings against Calheiros, who is suspected of embezzlement.

Eight of the court's 11 justices ruled that Calheiros must stand trial for allegedly misusing public funds nine years ago to pay for the financial support of a daughter he had out of wedlock.