Cho Kuk Photo: IC

An embattled law professor began his duty as South Korea's justice minister after receiving presidential approval on Monday, despite an ongoing probe by state prosecutors into alleged misconduct by his wife.

Cho Kuk was appointed to the role by President Moon Jae-in, the presidential Blue House said, with a mandate to reform the prosecutors' office.

Cho, a former human rights lawyer,  was named last month by the president as a nominee to lead the ministry.

But the confirmation process became a partisan battleground when questions were raised over Cho's daughter's schooling and his relatives' investment in a private equity fund suspected of dubious operations.

Officials from the prosecution office that Cho is to lead have carried out multiple raids over the past two weeks linked to the scandals.

Last week his wife Chung Kyung-sim was indicted for allegedly forging a college award for their daughter.

President Moon admitted in a televised statement on Monday that there was now a "sharp division" between critics and supporters of Cho, adding he had been "agonized" over the decision. 

But he said he stuck to his choice because it would leave a "bad precedent" if he had dropped Cho's nomination when it was not confirmed that Cho had broken laws himself. "I thought it was more important to follow principles and consistency," he said.

At his inauguration ceremony on Monday, Cho apologized for causing concern as he reaffirmed his commitment to implement reform.

"I have been tasked with a very important duty at a personally difficult time," Cho said. "My shoulders are heavy as I am well aware that an arduous and rough path lies ahead of us."

South Korea is an intensely competitive society where elite high schools have often been criticized - including by Cho, who has said they create a "more unfair society."

So he was slammed for hypocrisy when it emerged he had sent his own daughter to such an institution and that she had appeared to benefit from family connections.

Cho was grilled by lawmakers in a marathon 14-hour hearing on Friday, where he said he had "caused deep disappointment" and that his "words and actions were not consistent."