Security Minister David Mahlobo on Wednesday brushed aside an opposition call to resign over the jamming of the cellphone signal during the state-of-the-nation address, saying he could not be held responsible for an operational error.

Mahlobo told the National Assembly that since he had not ordered the signal blocking a question from Democratic Alliance (DA) intelligence spokesperson on whether he was prepared to quit was therefore "irrelevant".

"There was no executive authority... we have indicated that in terms of operational efficiency an error occurred, we regretted the error and on that basis we indicated our apologies that there was no intentional disruption of signal," Mahlobo said.

DA MP David Maynier, who likened the State Security Agency to East Germany's notorious Stasi, insisted that the minister bore ultimate responsibility and accused him of resorting to the "rogue official defence".

Mahlobo retorted: "One issue that we have indicated to all South Africans is an operational error and we ministers don't get involved in those."

When further pressed by Freedom Front Plus MP Pieter Groenewald, Mahlobo said there was a difference between executive and administrative responsibility and the opposition failed to understand it.

"It is understandable that some people are not understanding the role of the executive if you have never been in the executive."

The question session was dominated by the incident that prompted media houses to seek a court order that there would not be a repeat.

Referring to that case, both Mahlobo and Deputy President Cyril Ramaphosa repeatedly invoked the sub judice rule as a reason not to answer a raft of questions from the opposition on the tumultuous opening of Parliament.

This included a demand for assurances that police would not again be deployed in the National Assembly to remove MPs, which saw the Economic Freedom Fighters' (EFF's) Mbuyiseni Ndlozi told to leave the chamber after he repeatedly exclaimed: "You beat us up!" and refused to withdraw the remark.

Mahlobo initially asked that Maynier's question, plus another, put by the EFF's Sipho Mbatha, concerning the signal issue, stand over to a future date.

House Chairperson Thoko Didiza told members she had received a letter from Mahlobo concerning "certain matters" that were before the courts and said the rules of Parliament allowed that "the questions should stand over".

But opposition MPs prevailed after consultations on the matter.

However, earlier Ramaphosa said he had received legal advice not to speak on the issue as it was sub judice, and stuck to it.

"Hearings in relation to this matter will be happening in our courts in the next few days and for that reason I feel constrained to answer the question because the matters are before court," he said.

Ramaphosa was responding to a written question, posed by DA parliamentary leader Mmusi Maimane, on when Ramaphosa was made aware of the intended use of signal jammers, and other additional security measures, used during President Jacob Zuma's February 12 address.

He said: "As a matter of principle, I believe that it is correct we should have a free flow of information [in Parliament] and the incident that occurred here... should not be allowed and should not happen again.

"As regards the specific issues raised... I will be prepared to answer those once the legal cases have been concluded."

Ramaphosa repeated this answer three times, in response to follow-up questions.

This saw DA Chief Whip John Steenhuisen accuse the deputy president of "hiding behind" the sub judice rule.

"What has essentially happened here today is the deputy president has been allowed to hide behind a spurious interpretation of the sub judice rule, and the opposition has been denied the opportunity to exercise oversight over him," he said.

Earlier, Steenhuisen appealed to Speaker Baleka Mbete that members of the House "should be allowed to refer to a matter before a court, but should not be allowed to discuss the merits of a matter before the court".