Presiding Judge Joos Hefer described Ngcuka's alleged remarks, as revealed by former City Press editor Vusi Mona, as "gravely defamatory matter".
Mona went even further, calling the off-the-record meeting a "vitriolic character assassination" of those the national director of public prosecutions had named.
"At my age and experience I know the distinction between malicious gossip and a legitimate off-the-record meeting," Mona added.
He has since officially complained to the Constitutional Court, the Public Protector, the Human Rights Commission and Justice Minister Penuell Maduna.
Mona told Hefer that the controversial meeting took place on the evening of July 24 in a Sandton hotel. Ngcuka had called it and met with a selected group of seven black editors and one assistant editor.
He was concerned about this "racial exclusivity", Mona said.
He was brought under the impression that Ngcuka wanted to givebackground information on a widely circulated anonymous e-mail that contained allegations against him. However, the meeting turned out to be "wide-ranging".
Ngcuka used the event to violate citizens' rights, particularly their constitutional right to human dignity, under the guise of an off-the-record meeting, Mona testified.
These included Deputy President Jacob Zuma. Ngcuka allegedly revealed that Zuma could not meet his monthly financial obligations.
Regarding the National Prosecuting Authority's prima facie corruption case against Zuma, Ngcuka allegedly said he would wash his hands of the matter -- like the Biblical Pontius Pilate had done. Ngcuka would leave the case to be decided in the "court of public opinion", Mona maintained.
This apparently referred to Ngcuka's decision not to charge Zuma because the prospects of a conviction in court were too slim.
Mona further testified that Ngcuka had told the editors Zuma was in trouble because he had surrounded himself with "Indian people".
Ngcuka allegedly called former transport minister Mac Maharaj naive. This was because Maharaj maintained that payments he received from businessman Schabir Shaik was for work his wife had done for Shaik's companies.
Ngcuka said this unwittingly exposed Ms Shaik to tax evasion charges which he intended to bring against her, Mona maintained.
Further discussion during the meeting implied that Maharaj was willing to "sacrifice" his wife.
Ngcuka also alleged that the African National Congress, and particularly its youth league, was defending dubious white businessmen, Mona testified.
He said he decided to break the confidentiality agreement imposed at the meeting because he did not want to be party to the "character assassination".
He stressed that he was not taking sides in the fight between Zuma and Ngcuka. He repeated his belief that the anonymous e-mail against Ngcuka formed part of an unfortunate smear campaign.
Mona will retake the stand on Thursday for further cross-examination.
Meanwhile, it emerged that Deputy president Jacob Zuma will not complain before the Hefer Commission about the way in which Ngcuka's National Prosecuting Authority is treating him.
Hefer said at the beginning of the day's public commission hearing in Bloemfontein that he had been corresponding with Zuma's office on the matter.
From this it became clear that Zuma was not happy with the treatment he was receiving from Ngcuka's office. The deputy president nevertheless preferred not to use the commission as a forum to resolve this, Hefer said.
Zuma recently lodged an official complaint against Ngcuka with the Public Protector.
This followed the national director of public prosecutions' announcement that his department had established a prima facie corruption case against Zuma. Ngcuka nevertheless declined to charge Zuma for allegedly soliciting a bribe, because the prospects of conviction were too slim.
Hefer also announced on Wednesday that Zuma had informed him he was not part of an apartheid-era spy investigation against Ngcuka.
According to the deputy president his only knowledge of the spy claim against Ngcuka came from an earlier report that Mo Shaik had handed to him.
For this reason, Hefer said, he had decided not to subpoena Zuma to testify.
Hefer's comments left Mo Shaik, Ngcuka's main accuser, out in the cold.
Shaik served during the anti-apartheid struggle under Zuma's command in the African National Congress' intelligence operations.
His earlier testimony alleged that Zuma did take part in the investigation into Ngcuka as a suspected spy.
"I have reason to believe that (Ngcuka) is investigating (Zuma) now because he knew that (Zuma) had investigated him then," Shaik testified.
With this, he suggested that the NPA's corruption investigation against Zuma was in retaliation for the erstwhile spy investigation against Ngcuka.
Evidence so far before the commission indicated that Shaik was the sole source of the spy claim against Ngcuka. Shaik has called on the commission to ask Zuma for independent confirmation of the apartheid-era investigation into Ngcuka. He insisted that he had reported on the matter to Zuma - Sapa