Deltan Dallagnol, head of the Operation Car Wash task force, encouraged his colleagues to launch a secret investigation into Supreme Court Justice Dias Toffoli in 2016.
Deltan's effort is revealed in messages obtained from The Intercept Brazil and analyzed by Folha.
The prosecutor sought evidence that linked the justice and his wife to construction companies involved in corruption at Petrobras.
By law, lower court prosecutors cannot investigate members of the Supreme Court. At the time, Toffoli's decisions displeased the Operation Car Wash task force.
Deltan and Toffoli declined to speak. The task force reported that preliminary information exchange was common.
Translated by Kiratiana Freelon