President Jacob Zuma is ready to challenge the court ruling that corruption charges against him be reinstated.
A Zuma spokesman could not immediately confirm that the president had lodged an affidavit through his lawyers with the Supreme Court of Appeal, but the DA included a link to the document in a statement on its website.
The DA has been pursuing the matter in court and so would have access to such documents.
"President Jacob Zuma has this week filed his replying affidavit to the Supreme Court of Appeal," the DA said.
Zuma had been expected to take this route after an earlier appeal was rejected in June by the Pretoria High Court.
In April, a judge ordered a review of a 2009 decision by the National Prosecuting Authority (NPA) to set aside hundreds of charges against Zuma, describing the original ruling as "irrational". That decision allowed Zuma to run for president.
The scandals swirling around Zuma contributed to the worst election showing by the ruling African National Congress (ANC) in local polls this month and have triggered calls for his resignation.
The prospect of corruption charges being reinstated against Zuma follow a damning constitutional court judgment against him in March, which said he breached the law by refusing to refund some of the 240 million rand ($16 million) of state money spent on refurbishing his private residence.