The Oppenheimers’ $5,1bn sale of their 40% stake in De Beers to Anglo American was in effect a disinvestment from South Africa, the chairman of Parliament’s mineral resources committee, Fred Gona, charged on Wednesday.

His concerns echo miners’ unease about South Africa as a destination for investment after calls by the African National Congress Youth League for mines to be nationalised. Recently, large resource groups announced they were scaling back their interests in South Africa.

Mr Gona said the Oppenheimers’ withdrawal from the diamond producer after a history of nearly 100 years of mining was a "seriously worrying sign that they have lost confidence in South Africa".

"We have been trying to understand the reasons for this, and until now have not been able to establish why," he said in an interview during the mineral resources committee’s public hearings on the implementation of the mining charter. Mr Gona said the family’s "disinvestment" followed the sale or closure of several South African mines by De Beers over the past few years.

Mr Gona held onto his view despite assurances from Nicky Oppenheimer last week that the family was not abandoning South Africa. "The Oppenheimers are not turning their back on South Africa," he said. "This is where we operate from as a family and we’ll continue doing so. If anything, we’ll be making further commitments to South Africa and Africa."

Mr Gona was also upset that De Beers Consolidated Mines CEO Phillip Barton insisted two days before the announcement of the Oppenheimer deal that De Beers had no intention of disinvesting from South Africa. This was tantamount to concealment, he believed.

"They led us to believe that nothing was going to happen," Mr Gona said.

BHP Billiton South Africa executive manager Ravi Moodley told MPs on Wednesday that the group’s recent and planned investments in its manganese and coal operations — which amounted to several billion rand — were proof it intended to stay in South Africa. The group said it had invested R6,8bn in expanding its Douglas coal mine and R600m in a new coal mine at Klipspruit.

A further R1,5bn expansion of the Wessels graben manganese mine would depend on the outcome of a feasibility study.

Future projects included the R800m Hotazel town development and the R714m M14 project to add another furnace to the manganese smelter.

"We are very much here to stay," Mr Moodley said. With Allan Seccombe