Gwede Mantashe says the differences between the public protector's Nkandla findings and that of the interministerial task team are cause for concern.
The ANC has stated publicly its support for public protector Thuli Madonsela's office and her report on Nkandla, but elements within the party are taking a more hardline stance.
The party's secretary general, Gwede Mantashe, has hinted at a court challenge and said the difference between her findings and that of the interministerial task team was a cause for concern that needed to be resolved by an appropriate state institution.
He told the Mail & Guardian that "a court of law is the most appropriate" avenue. He added that he did not mean a judicial review, but a court challenge would amount to the same thing.
ANC Youth League convener Mzwandile Masina told the M&G that the league would motivate in ANC structures for the public protector's report to be taken on review.
The acting leadership of the league came out fighting, calling for Madonsela's resignation, saying she acted in concert with opposition parties to damage the ANC ahead of the national elections.
'South Africans are not stupid'
"She has been frequenting DA [Democratic Alliance] tea parties, attended their rallies, and we must say at this point, South Africans are not stupid," said ANC Youth League leader? Mzwandile Masina at a press briefing on Thursday. He added that his organisation had not engaged with Madonsela, calling her arrogant.
"She can conclude this process and immediately after that she must leave ... She has caused enough damage and continues to poison the minds of South Africans."
In contrast, the ANC treaded carefully in their response to the report at an earlier media briefing on Thursday, welcoming its release but reiterating their allegiance to the findings of the interministerial task team.
The differences between the two reports have become a point of disagreement.
The task team, which the ANC spokesperson said was a legal entity accountable to Cabinet, released their own report in December 2013.
- Read the government task team's full report
They insist that the building of the "fire pool", chicken run, cattle kraal, visitor's centre, amphitheatre and more using public funds was necessary for Zuma's security, using often comical reasons to justify their need.
However, Madonsela's report dismissed these justifications and found that Zuma had to pay back a portion of the costs.
The ANC seems to agree on paying back the costs, saying on Thursday that Zuma would consult the ministers noted in the report to determine the portion he must pay.
But they took issue with the difference in findings between the two reports and the challenge it poses.
"Areas of disagreement ... must be addressed and reconciled by government. If agreement cannot be reached within a short space of time, competent institutions of state must review the reports and make a determination."
The party was careful to point out that they could not force an institution like Parliament to review the differences, and that the relevant institution head had to make a decision.
But Zuma is entitled to take the matter on judicial review and would have to institute the proceedings in a court of law if he chose that route.
Mantashe seemed to think the court of law was the best route. "Once they disagree, shouldn't fight it out in public, they should subject it to legal review and come to a determination and say if this is the right approach it should be followed to the conclusion," he said off the cuff while reading from the press statement.
Former KwaZulu-Natal premier Zweli Mkhize was more cautious however and would not be drawn on whether a court should review the differences, adding that it should not be an adversarial process.
"We leave that to government because whether it is a Parliament, court of law or any other institution, all we are making a statement on is that this is very new democracy," he told the M&G.
For Mkhize, it was more of an academic matter. "Just as a matter of principle: how do you deal with two state institutions coming to different conclusions?" he said, adding that an appropriate body should make the findings and move on. "I shouldn't be seen as a hostile thing ... it's in support of our democratic processes and accountability and transparency."
The ANC would not be drawn on whether the public protector's report should constitutionally carry more weight than the task team report, saying only that government had to do its work and come to its own conclusion and couldn't wait for the public protector.