The Organisation Undoing Tax Abuse (Outa) on Monday called on advocate Busisiwe Mkhwebane to vacate her post as public protector after a damning Constitutional Court ruling against her.

Mkhwebane on Monday endured a scathing assessment of her report on the South African Reserve Bank (SARB) from the Constitutional Court (ConCourt), which found that she had lied and used false documents to advance her cause.

The ConCourt said Mkhwebane acted in bad faith, her entire model of investigation was flawed and she was not honest, ordering her to pay the punitive personal costs originally ordered by the High Court. 

Mkhwebane had appealed the High Court order that she should, in her personal capacity, pay 15 percent of the SARB's costs on an attorney and client scale, including the cost of three counsel.

After Monday's ruling, the public protector must now pay the costs which stemmed from the SARB's challenge against her report on its role in the apartheid-era bailout of Bankorp investigation.

"The ConCourt judgment against her is damning. She can no longer continue in that role," Outa's head of legal affairs, advocate Stefanie Fick said.

"Her pushback against accountability measures by Parliament further underlines her lack of understanding of her role."

Delivering judgement on Monday, Justice Sisi Khampepe said the ConCourt held that there was no sound basis to justify the interference with the High Court's discretion to award personal costs against her.

In June, Outa petitioned Parliament for an inquiry into Mkhwebane's fitness to hold office as public protector due in the face of adverse court judgments against her.