ANC Treasurer General Zweli Mkhize says those implicated in the #GuptaLeaks need to account.
He said they should subject themselves to a commission of inquiry so the country can find out the truth behind continuing claims that the country has been captured.
Mkhize delivered an Oliver Tambo Memorial lecture in Katlehong on Thursday as part of a series of events the governing party is holding throughout the year to celebrate what would have been its longest serving president's centenary.
"These emails that have come out and all the statements that we read in the media are a huge embarrassment," Mkhize said.
The Treasurer General was referring to a trove of leaked emails which put the Gupta family, who are well known friends of President Jacob Zuma, at the heart of a project which attempted to capture the country's president and state owned enterprises.
The #GuptaLeaks show evidence of corruption, kickbacks and political influence the Gupta family had over some members of the executive and directors of SOEs.
Mkhize, who has been punted by some as a "third way" and possible compromise president in the battle to lead the ANC, rejected state capture and said those who were involved in it knew what they were doing. He said the party did not want to be tarnished along with them.
"I think it's important also that we say to ourselves, for those whose names are being raised in these emails, we expect that they will come forward and clear their names," he told the crowd.
He told crowds made up mainly of pensioners and the youth that there were three issues causing tensions among alliance partners in the liberation movement.
He listed state capture, calls by alliance partners, SA Communist Party and labour federation Congress of SA Trade Unions' calls for President Jacob Zuma to go and the succession race ahead of its 54th national conference in December.
Branches do not allow your power to be taken away
He called on everyone to join in the calls to reject state capture.
"We as the ANC consider any form of capture, whether by individuals, families, companies or any foreign governments or whatever as a form of corruption. It's the subversion of the will of our people and we will not accept it," said Mkhize.
Mkhize also spoke at length about the role of the branches, reminding supporters that they needed to unite the 105-year-old liberation in honour of Tambo, the ANC's longest serving president.
Speaking out against negative tendencies which had crept into the party, he called for an end to factionalism and gate-keeping.
"Factions and divisions act as a Berlin Wall for those who want to continue with corruption," said Mkhize.