African National Congress (ANC) secretary general Gwede Mantashe says he and other senior party members who spoke out against President Jacob Zuma's cabinet reshuffle were never asked to apologise at the party's NWC meeting earlier this month.

"No there was no apology. We were not even asked to," he told radio 702 on air on Wednesday.

"We had a discussion which was very fruitful and very constructive. Nobody was asked to apologise."

He was referring to the party's national working committee meeting on April 5.

On Friday, Zuma's lawyers filed heads of arguments to the Constitutional Court in the United Democratic Movement's bid for a secret ballot in the upcoming motion of no confidence against him.

Reference is made to Ramaphosa and Mantashe's "public apology" for speaking out against Zuma's decision to reshuffle his Cabinet on March 30. It was the president's prerogative, they apparently said.

NWC member Derek Hanekom said on Twitter that both Mantashe and Ramaphosa were not asked to apologise at the meeting.

"That is perfectly true. I was at the NWC meeting. There was nothing to apologise for," Hanekom tweeted.

Mantashe said Zuma's legal team needed to clarify what they meant by claiming he and Ramaphosa had apologised.

Presidency spokesperson Bongani Ngqulunga said it was not practice for them to comment on a matter before court.

He did, however, say the claim about Mantashe apologising was not in Zuma's replying affidavit filed a week earlier. It was only in the heads of argument Zuma's lawyers had filed.

The lawyers could not immediately be reached for comment on Wednesday.

ANC discipline not a threat to MPs

According to the papers, Zuma said it was a mistake to think party discipline could serve as intimidation of ANC MPs during the vote.

"It is incorrect to suggest, as the applicant does, that the president is confusing his role as the president of the ANC and his role as the president of the republic.

"It is trite that the legal effect of our constitutionally determined political system is that members elected on party lists who are allocated to legislative bodies under a...  system of proportional representation are accountable to their respective parties and Parliament.

"The party is accountable to the electorate."

MPs were therefore obliged to remain loyal to their party decisions, as the party was ultimately accountable to its voters.

"The obligation of loyalty to party is not inimical to the notion of an accountable, responsive, open and democratic government. The ANC is in no different a position."

Zuma said the court could not preclude a political party from taking disciplinary steps against a member who violated its constitution.