Public Protector Busisiwe Mkhwebane has found that National Treasury Director-General Dondo Mogajane failed to disclose that he has a criminal record when he applied for the position in 2017.
Mogajane was found guilty of contravening the Road Traffic Act in 2011.
An anonymous complaint was laid in August 2017 with the Public Protector after Mogajane applied for the Treasury top job.
"Mr Mogajane had a duty in law to act honestly and in good faith towards his employer, where he was required to disclose this," Mkhwebana said on Wednesday.
Mkhwebana said that, during her investigations, she had found that former finance minister Malusi Gigaba's conduct in the appointment of Mogajane was improper.
"Evidence presented before me confirms that former minister Malusi Gigaba knew, or ought to have reasonably known, about Mr Mogajane’s failure to disclose the criminal record in his Z83 application form."
Gigaba had approved the filling of the position, thereby "tacitly" condoning the impropriety, she said..
"Former Minister Gigaba’s conduct was, therefore, irrational and unreasonable under the circumstances, and consequently amounts to improper conduct as contemplated by Section 6(4) of the Public Protector Act, 1994.”
In her remedial action, Mkhwebane has asked President Cyril Ramaphosa to take appropriate disciplinary action against Mogajane for blatantly and dishonestly making a false representation of material facts.
She ordered that Ramaphosa act within 30 days.