An ex-director of Brazil's state-run oil company Petrobras is reported to have accused more than 40 politicians of involvement in a kickback scheme.
Paulo Roberto Costa - who is in jail and being investigated for involvement in the alleged scheme - named a minister, governors and congressmen.
Among them were members of the governing Workers Party and groups which back President Dilma Rousseff.
But the names, published in a magazine, also included rivals of Ms Rousseff.
Many of the names were published in Veja, one of Brazil's leading magazines, just weeks before the presidential election in which Ms Rousseff is running for a second term in office.
Several politicians mentioned have denied involvement.