Folha de Sao Paulo reported Monday Federal Deputy Roberto Jefferson accused the ruling Workers' Party, or PT, of giving some lawmakers up to R$30,000 (more than $12,000) a month for them to back PT initiatives.
The money was allegedly paid out by the PT's treasurer. The party denies the accusation.
Jefferson, whose Labor Party is an ally to the PT, is currently embroiled in a corruption scandal involving Brazil's post office.
President Luiz Inacio Lula da Silva has been sticking up for Jefferson in recent weeks trying to thwart efforts in the Congress to begin a legislative investigation.
Analysts said the lawmaker's accusations already caused damage Monday on the economic front, as both Brazil's leading market index the Bovespa and its currency took sharp losses.