Public Enterprises Minister Lynne Brown has announced that Dr Ben Ngubane has resigned as nonexecutive director and chairperson of the Eskom board with immediate effect.

“Dr Ngubane formally tendered his resignation, which I accepted,” Brown said in a statement released late on Monday night.

“To ensure continuity at Eskom, I have decided to appoint Mr Zethembe Khoza as interim chairperson until I am able to take new board appointments to Cabinet for approval,” Brown said.

Eskom’s annual general meeting is scheduled to take place on June 23 and the Minister indicated previously that the board will be "rotated" at that meeting.

Brown made no announcement, however, about who would be appointed interim CEO, after the controversial decision to reappoint Brian Molefe was rescinded at the end of May.

Matshela Koko, who was appointed interim CEO when Molefe stepped down in January in the wake of a damning Public Protector report, is currently on leave, while a forensic and legal investigation into a potential conflict of interest relating to Koko’s stepdaughter, Koketso Choma, is being finalised.

The probe is meant to be completed in May, but the timeframe have been extended by the board at the request of the firm of attorneys investigating the matter. "In the interests of the process, the interim group chief executive has decided to take leave until the investigation is finalised in mid-June," Brown said last month.

The National Union of Mineworkers (NUM) welcomed Ngubane's resignation, but also called for the immediate resignation of all other remaining board members.

"They are a disgrace to both Eskom and the government. We need men and women with integrity who will also care about the well-being of the employees, who are the only source of 'lights on' agenda.  As they all resign, we must also call upon the government to be decisive and come out very clear on the issue surrounding the reversal of closure of the five power stations as pronounced by Brian Molefe on his short return to Eskom before his reappointment was rescinded," the NUM said in a statement.

Trade union Solidarity also welcomed the resignation, with deputy general-secretary Deon Reyneke describing Ngubane's departure, together with the reversal of Molefe’s reappointment, as steps in the right direction.

However, he said Eskom was in need of a more extensive clean-up. “We hope this step constitutes the beginning of a new accountability within Eskom, since the board has made a few strange decisions lately."