By Steve Kingstone
BBC News, Sao Paulo
The former treasurer of Brazil's governing Workers' Party has admitted publicly that the party broke the law when financing election campaigns.
Mr Soares insists he acted alone
Delubio Soares said campaign funds totalling $17m (£10m) had not been declared to the electoral authorities.
He was speaking at a parliamentary hearing into alleged corruption.
Mr Soares quit as the treasurer in July after accusations that he organised bribes which were allegedly paid to MPs in return for political support.
By his own account, Mr Soares had a secret war chest of $17m which funded election campaigns between 2002 and 2004.
The money was supplied by a businessman and the funds were never declared to the electoral authorities in violation of Brazilian law.
In his evidence to the parliamentary hearing, Mr Soares insisted he had acted alone, without the knowledge of the president or the broader party executive.
He said off-the-books funding was common among Brazil's political parties.
Most commentators would agree with that. But they also agree this is the most serious corruption scandal in Brazil for more than a decade.
Beyond electoral crimes, Mr Soares is accused of bribing lawmakers from other parties to support government legislation. He continues to deny that claim.
But later on Wednesday, the party's new leadership expressed support for a police investigation into suspect cash payments which were made to politicians and their advisors in the days before key parliamentary votes.
This escalating affair has tarnished the reputation of the Workers Party, which won power by promising honest government.
But as yet, the allegations have not seriously damaged the president, Luiz Inacio Lula da Silva.
In opinion polls, support for him has held firm, even as trust in his party slips away.