"These terms are just fancy words for theft from the poor. They are fancy words for ordinary South Africans subsidising an international conglomerate, BHP Billiton, to the tune of R4.8bn a year — exported from this country in the form of aluminium ingots," Mr van Dalen said.

BHP and Eskom did not reply to requests for comment.

Mike Rossouw, chairman of the Energy Intensive Users Group of South Africa — whose members account for 44 percent of the electricity consumed in the country — said special pricing agreements were made on a "willing buyer, willing seller" basis. He said Eskom relied on big users such as BHP to relieve the constrained electricity system through power interruptions.

Mr van Dalen said BHP’s aluminium smelters were built when there was excess electricity.

"Eskom wants us to believe that we are stuck with these contracts for 25 years; that they were inherited from the apartheid era pre-1994. I asked questions in Parliament on this. The answers revealed that some of the deals were signed as late as 2003."

He said Parliament must call for the cancellation of the deal.

Mr Greyling said the contract was costing South Africa billions of rand. "We also want public pressure to be brought to bear on this company to force it to the negotiating table so that we can get a better deal for all South Africans."

African National Congress MP Willem Koornhof said the two statements had nothing to do with the report tabled, and accused Mr van Dalen and Mr Greyling of "political grandstanding".

Tristen Taylor, project co-ordinator at Earthlife Africa, said the deal was "illegitimate, if not illegal".

"It is appalling that BHP Billiton, a multibillion-dollar company, is being subsidised by South African electricity consumers," he said.

With Siseko Njobeni