The next African National Congress (ANC) caucus will not repeat the mistakes it made in the Fifth Parliament, as it did when it failed the Constitution by not holding former president Jacob Zuma to account about Nkandla, ANC chief whip Jackson Mthembu has vowed.

Mthembu addressed the media on Thursday after the Fifth Parliament's final ANC caucus meeting, which was addressed by President Cyril Ramaphosa.

He said Ramaphosa had thanked them for "work well done" and for "keeping the executive on its toes".

"The president appreciated that we did not kowtow. We continued to do our work, making this Parliament an activist Parliament," Mthembu said. The question was put to Mthembu that the Constitutional Court had found that the National Assembly's handling of the Public Protector's report on Nkandla "was inconsistent with the Constitution and unlawful".

Mthembu said that, at an ANC caucus lekgotla, they had committed that "never and never again, we as an ANC caucus will do anything that is illegal".

He said they would continue to hold the executive to account.

"Of course, we are just human. We have committed errors. A commitment we make is that we will not commit errors again."

He said the ANC was the only party that admitted to its mistakes.

"You know, we are not an ostrich," Mthembu said.

"With that bioscope, we should not have done that," he said in reference to the bizarre video in which a sweating former police minister Nathi Nhleko tried to convince South Africans that the swimming pool at Zuma's house in Nkandla was, in fact, a "firepool", and therefore a necessary security measure. Nhleko is currently an ANC backbencher.

He said the mistakes they had made in this term had "laid the basis for the next ANC caucus to say no".

"History will continue to judge us harshly if we cannot learn lessons from wrongdoing."

Mthembu said they had refused to do many things since the Nkandla matter.

"We won't tell you what those are!" he added, with a smile.

Mthembu also admitted that the ANC caucus was concerned by recent polling results, but said it would galvanise the party to work harder. He remains confident that they would be back as the governing party after May 8.

"There is no way we cannot be worried," Mthembu said.

"When we are worried, we even forget about our factions. When we are worried, we get to work."

He said the ANC's visibility on the ground was only starting to kick in now.

"When ANC visibility is in full force, we know polling will reflect this gigantic movement."

Asked why Zuma still campaigned for the ANC, Mthembu said the former president was a member of the party in good standing and hadn't been found guilty of anything.

"In renewing an organisation, we shouldn't be above the rules of natural justice."