The ANC says the public protector's office was responsible for the provisional report leak and called for the final version to be published soon.
The ANC believes the leaking of public protector Thuli Madonsela's provisional report into Nkandla came from her office, and said it is concerned about the "regularity" with which provisional reports of this kind are leaked.
On Friday, the Mail & Guardian published details of the provisional report, which called for President Jacob Zuma to repay the state money spent on his home and accused him of lying to Parliament.
At a press briefing on Tuesday, ANC secretary general Gwede Mantashe called for the final report into Nkandla to be released "with immediate effect", but especially before the 2014 elections.
He said if Madonsela were to release the report just before the elections, this would reveal her political intentions because "then it becomes a political factor and weighs into elections".
Deputy secretary general Jesse Duarte was more overt in her belief that Madonsela herself was responsible for the leak.
Duarte accused Madonsela of "enticing debate" about issues she was investigating and said she "seemed a bit comfortable" with the fact that the report was leaked.
She also said Madonsela, by publicly saying she would take measures to mitigate potential leaks from her office on Monday, had inadvertently admitted to being the source of the leaks.
But in the statement referred to by Duarte, Madonsela did not say this. Instead, Madonsela said these measures meant that affected and implicated parties would no longer receive provisional reports, implying that the leaks stemmed from these parties, and not her office.
"In terms of the new arrangement, affected and implicated parties will no longer get full provisional reports. Instead, they will be furnished with information or parts of the report that relate to them for purposes of soliciting their comments.
"This is hoped to stem the trend of purported leakages, which puts the integrity of investigations in jeopardy, while also prejudicing the people whose names are mentioned in the reports."
Meanwhile, Mantashe said the ANC had instructed government to make available to the public all experts who decided and designed all elements of the security features at Nkandla.
"These experts must explain their decisions and designs in the public domain," he told reporters in Johannesburg.
"This must be done to ensure that all and any queries that the public may have with regard to these particular issues are tabled and responded to exhaustively."
He said the ANC wanted Madonsela to clarify whether Zuma requested any security upgrades to his homestead.
"Did President Zuma request that a swimming pool and kraal be built and that his wife's tuck shop be moved from its original position?"
The ANC did not ask Zuma these questions during its meeting on Sunday and Monday, because he was not conducting the investigations, Mantashe said. – Additional reporting by Sapa