Deputy President Cyril Ramaphosa has told Democratic Alliance (DA) MPs that are critical of President Jacob Zuma that they shouldn't be so quick to cast the first stone on "ethical mishaps".

DA MP Charles Motau asked Ramaphosa during a question and answer session if he believed South Africa could "break from the moral decay" under the leadership of Zuma and his government.

"We should never try to be holier than thou, or holier than other people," Ramaphosa answered Motau in the National Assembly on Wednesday.

"Things like mishaps in ethical behaviour can happen to anyone, to any organisation.

"When they do happen, clearly they need to be properly processed and addressed. That is the important thing that we should focus on."

DA caucus members could be heard shouting back, "A mishap?", "Are the Guptas mishaps?" and, "Your answer is a mishap".

"In the end, our commitment to our values, which are enshrined in our Constitution, should be our lodestar," he continued.

"Can we live up to that? I would say yes."

He again told DA members to use the Constitution as "bedtime reading".

"Don't forget the president," members of the DA caucus shouted again.

State capture revelations 'undermining confidence'

Ramaphosa was originally answering a question from African Christian Democratic Party leader Kenneth Meshoe.

Meshoe had asked what contribution Ramaphosa was making to restoring ethics and morals in politics during the country's "time of crisis".

"The ... revelations about the ongoing corporate capture have undoubtedly and understandably undermined public confidence in the country's leaders.

"That we have to admit," Ramaphosa had answered earlier.

"It is therefore essential that these allegations are thoroughly investigated as a matter of urgency through a credible process."

He repeated government's call to establish a judicial commission of inquiry.

"The law should also take its course without fear or favour."

He also said the restoration of moral and ethical leadership was the responsibility of all leaders in society, including elected officials, public servants, community leaders and civil society activists.

"Now is the time for these people to come to the fore and get engaged in active citizenry.

"This is not a responsibility that can fall on one person. It falls on all our shoulders. It falls on all of us here."

Ramaphosa 'flogging a dead horse'

Agang SA MP Andries Plouamma followed up, and said Ramaphosa seemed to be flogging a dead horse, and losing his integrity.

He asked him to "break from the yoke the president has bound him with".

"Why do you continue to legitimise the president's behaviour? Why are you giving the country a death sentence?

"Why are you allowing the president to turn you into 'n arme skepsel [a poor wretch]?"

Ramaphosa skillfully beat the question down.

"Madam speaker, I don't know what the actual question is. I don't have my Afrikaans dictionary today to remember what an arme skepsel is.

"All I can say is, I am not a skepsel," he told Plouamma with a smile.