State corruption in South Africa is now having a global impact: First it was the British PR firm Bell Pottinger and then the auditing giant KPMG.

Now the global consulting firm McKinsey has found itself dragged into a vast scandal involving allegations that government and business elites are looting public institutions.

It has been asked to pay back tens of millions of dollars that it earned working in South Africa.

The country’s energy utility, Eskom, said the money had been paid unlawfully and should be refunded .

McKinsey, working with a controversial local company, cut a deal to advise Eskom in 2015.

McKinsey was paid almost 1bn rand ($70m, £50m) for a few months’ consultancy work. Its local partner, Trillian, earned half that sum.

Now Eskom itself has said that the deal was dodgy, and McKinsey should return the cash.

But McKinsey insists it did nothing wrong, and that it withdrew from the deal as soon as it became suspicious.

This scandal, like so many in South Africa today, involves allegations against the Gupta family – powerful businessmen accused of buying influence over President Jacob Zuma, members of his cabinet and other key officials.

All deny any wrongdoing.

The fact that international firms are allegedly involved has helped to focus attention on South Africa’s growing corruption problem.

KPMG is battling to save its reputation and business here.

Bell Pottinger is facing bankruptcy.