The DA has slammed the public protector's findings on tweets made by its Western Cape premier, Helen Zille.
However, the party has maintained its distance from the content of Zille's tweets, saying it still does not condone them.
In her report, Mkhwebane held that Zille had breached the Executive Members Ethics Code, when she tweeted in 2017: "For those claiming that the legacy of colonialism was only negative, they should look at various aspects of South Africa's development, such as the judiciary and other infrastructure."
In her recommendations, Mkhwebane directed the speaker of the Western Cape provincial legislature to sanction Zille.
In a statement on Tuesday, the DA chief whip John Steenhuisen said the report on Zille adds to the "growing list of abject findings" by Mkhwebane.
"It is on the basis of her fundamental misunderstanding of the basic principles of the Constitution and her own powers, that her findings against [Zille] are now part of this growing list of abject findings by her. Her findings have no basis in law, and if unchallenged have profoundly negative constitutional implications," he said.
"The content of [Zille's] tweets was the subject of a settlement between her and the party, and resulted in a public apology from [Zille]. The party has made it clear that we did not in any way support the merits of the tweets at the time. This stance remains unchanged. We have never condoned the content of [Zille's] tweets."
"However, this ruling has profound constitutional implications, which speak to Mkhwebane's fundamental misunderstanding of the powers of the public protector."
Steenhuisen said the DA will on Wednesday present its case on Mkhwebane's fitness to hold office, when she appears before the parliamentary portfolio committee on justice.
"Through her conduct, she has demonstrated that she is unable to act lawfully, she consistently acts without regard to procedural fairness, and that her findings are patently unreasonable. The DA will fight to protect this vital constitutionally established institution and ensure that its integrity is restored by removing Mkhwebane and ensuring that a suitably qualified person is appointed to the office," Steenhuisen said.