"You are an idiot," DA MP David Maynier told Defence Deputy Minister Kebby Maphatsoe on Tuesday.

The insult was delivered in the National Assembly, after Maphatsoe seemingly denied in the House that he had labelled Public Protector Thuli Madonsela a spy working for the US Central Intelligence Agency (CIA).

Maphatsoe's alleged comment, which has sparked a diplomatic row, was reportedly made at the weekend during the unveiling of a military veteran's tombstone in Soweto.

On Tuesday, the deputy minister, who was responding to an earlier statement by Democratic Alliance parliamentary leader Mmusi Maimane, told MPs: "I reject the allegations about what I said on Sunday, in the newspapers. I refer all others to the record."

At this point, he was stopped from speaking by Deputy Speaker Lechesa Tsenoli, who wanted to know who in the opposition benches had used the word idiot.

"Who shouted: 'You're an idiot'?" he enquired, adding that this was "out of order".

Maynier admitted using the term.

"Speaker, I shouted idiot because the honourable deputy minister of defence is an idiot for saying what he said," he explained.

After hearing various points of order, Tsenoli ordered Maynier to withdraw his reference to Maphatsoe being an idiot.

Maynier responded: "Deputy Speaker, with respect, I am not going to withdraw my remark because I'm simply saying what most South Africans believe about the deputy minister's statements in respect of Thuli Madonsela."

Tsenoli then warned him that if he refused to withdraw, he would have to leave the House.

"Deputy Speaker, I refuse to withdraw my remark that the deputy minister of defence is an idiot, because he is an idiot," Maynier told him, to shouts and laughter across the House.

Tsenoli then ordered him out, and Maynier left.

Maphatsoe later expanded his earlier remarks, following a call by Maimane for him to clearly confirm or deny what he is reported to have said at the weekend.

"On Saturday, September 6... in White City... where we were unveiling the tombstone of one of our heroes... the journalist who reported that article of the Star [newspaper] on Monday was not at that event.

"He used secondary documents, which we have record of.... That's why I am saying if people want to have the record of what happened and what I said on Saturday, I have got those records.

"So I stand by my statement that I made on Saturday in that event.... So what is happening in the newspapers, and if people read correctly, there is nowhere in the newspaper, in The Star, where there is mention of the Public Protector being a Central Intelligence Agency spy."

Maphatsoe said it was "just a headline, and by a person that was not there".

He said the journalist had admitted to him, via sms, that he was not at the event.

"So what we are reading here... the person was not present. So I stand by my statement... I reject the allegations levelled against me," he said.

Madonsela has given Maphatsoe a 72-hour ultimatum to retract his allegation that she is a spy for the CIA, or face legal action.