It was not up to the African National Congress (ANC) to decide whether its investment arm, Chancellor House Holdings, should get rid of its stake in Hitachi, party secretary-general Gwede Mantashe said on Tuesday.

"Whether we are going to dispose of our stake... I don't think that decision should be taken in Luthuli House because you have got a company which is having a board," he told media in Boksburg.

Mantashe was speaking after "brutal" and "candid" talks with ANC alliance partner the Congress of South African Trade Unions (Cosatu) at Luthuli House, the ANC headquarters in Johannesburg, on Monday.

Cosatu had criticised the ANC's involvement in Hitachi with its general secretary Zwelinzima Vavi saying that if it was true that the ruling party had such a stake, then "God help us all".

Hitachi Power Africa was awarded a multi-billion rand contract for Eskom's Medupi power station.

Chancellor House Holdings (CHH) owns a 25% in Hitachi.

"That decision [on whether to sell its stake] must be taken at that level rather than our level, that's the right thing to do," said Mantashe.

"If we begin to manage the investment company from Luthuli House it is likely to be more inefficient.

"But if it is run by its management team under the guidance of the board it will take proper decisions depending on what is in the interests of the company."

Mantashe distanced the ruling party from decisions taken by CHH, after opposition parties raised objections to the ANC's involvement in Hitachi, citing it as a conflict of interest due to the Eskom deal.

"The ANC has no stake in Hitachi, we invest in Chancellor House. Full stop. Where Chancellor House invests doesn't translate into ANC having a stake," Mantashe said.

"Chancellor House may have a stake. That is economics 101."

Mantashe's comments came after ANC treasurer general Mathews Phosa reportedly said the ANC would sell its share in Hitachi.

However, reports on Tuesday quoted CHH managing director Mamatho Netsianda as saying via sms: "Please do not call me. The official position is: Chancellor House Holdings is not selling its stake in Hitachi Power Africa."