The Democratic Alliance (DA) said on Tuesday corruption watchdog the Public Protector would, at its request, investigate beleaguered Finance Minister Nhlanhla Nene.

Nene has faced growing calls to resign over his involvement with the controversial Gupta family, and last Friday apologised for not disclosing early and fully the details of his meetings with them, saying he realised this cast a shadow on his conduct as a public office bearer.

Nene said he was glad that a commission probing allegations of graft by government officials and executives from state companies under former President Jacob Zuma's leadership was looking into allegations of his involvement and that of his family.

On Tuesday DA shadow minister of finance David Maynier said he had asked Public Protector Advocate Busisiwe Mkhwebane to probe Nene in terms of the Executive Members Ethics Act, to determine whether he breached the executive code of ethics applicable to ministers and deputy ministers in South Africa.

"The alleged breach of the executive code of ethics relates to allegations surrounding a Public Investment Corporation investment in S&S Refinarias, which reportedly included a US$ 1.7-million “referral fee”, which may have benefited the minister’s son, Siyabonga Nene," Maynier said.

"I received a reply from Oupa Segalwe, Acting Executive Manager: Communications & Stakeholder Management, dated 08 October 2018, confirming that the matter will be investigated by the Good Governance and Integrity Branch within the Office of the Public Protector."

He said the allegations were serious given the fact that, in terms of the Constitution, ministers may not “expose themselves to any situation involving the risk of a conflict between their official responsibilities and private interests”.