There is no evidence that the debate on whether the government should take over South Africa's mines is hurting investment in the sector, Minerals Resources Minister Susan Shabangu said on Wednesday.

Based on the feedback from various sources including meetings during the road-shows and promotional activities, there is no evidence that there is a trend of disinvestment due to the nationalisation debate, Shabangu said in a written reply to parliamentary questions.

Government has been at pains to re-assure investors that it would not nationalise mines, after calls by the youth wing of the ruling African National Congress that such a policy would improve the lives of the poor.

Other cabinet members have said the debate has undermined confidence and deterred investment.

Shabangu has said mine nationalisation in the world's largest platinum producer was not government policy.

Economists said nationalisation could bankrupt Africa's largest economy, with the bill for taking over all mining firms equal to about two-thirds of GDP or twice the annual national budget.

Threats to tweak laws in order to expropriate shares for a fraction of their value would run up against international investment guarantees that would almost certainly trigger severe backlashes from South Africa's trading partners.

But the idea resonates with the country's poor black majority who see it as a way to spread the wealth from a sector that grew powerful along with white-minority apartheid rule.

President Zuma on Tuesday said open debate within the ruling party about social and economic issues cannot be stifled, and all views should be aired, no matter how controversial.