Brazil's Prosecutor-General Rodrigo Janot asked the country's Supreme Court on Monday to open an investigation into opposition Senator Aecio Neves, amid ongoing corruption probes concerning many politicians.
Neves was previously included in a list of 50 politicians for allegedly taking bribes from state-run companies.
The Prosecutor-General had stopped the investigation of Neves last year but is now asking for it to be reopened based on plea bargain testimony from Delcidio do Amaral.
Amaral, the government's former leader in the upper house of Congress - who is now serving as a senator - said that Neves benefited from a corruption scheme involving Furnas, a subsidiary of state-run power utility Eletrobras.
The scheme was similar to one that police uncovered at state-run oil firm Petroleo Brasileiro SA, known as Petrobras, claimed Amaral.
Construction executives worked together to overcharge Petrobras for work and used the excess funds to bribe politicians.
A spokesman for Neves, the leader of the centrist Social Democracy Party (PSDB), said the investigation would show his conduct was correct.
Neves has competed with President Roussef in 2014 elections, but lost by a narrow margin.
The prosecutor also asked for an investigation of congressman Marco Maia.
Maia, who is from the ruling Workers Party, said he was the "victim of a lie."