FILE PHOTO - A Barclays logo is pictured outside the Barclays towers in Johannesburg, South Africa, December 16, 2015. REUTERS/Siphiwe Sibeko/File Photo

JOHANNESBURG (Reuters) - Barclays Africa BGAJ.J and Standard Bank SBKJ.J said on Monday they would stop working with McKinsey, a further blow to the global consultancy as it faces allegations of bribery for work done with friends of South African President Jacob Zuma.

Privately-held McKinsey, the world’s largest management consultancy, has denied doing anything illegal but said this month that it was embarrassed by mistakes it made while working with South African state utility Eskom last year.

McKinsey said it regretted working on a 1.6 billion rand ($113 million) contract at Eskom alongside a company controlled by the Gupta family, wealthy friends of President Zuma who are accused of unduly influencing government contracts.

Zuma and the Guptas deny wrongdoing.

Barclays Africa and Standard Bank told Reuters in separate emailed responses to questions that they would terminate their relationships with McKinsey without giving reasons.

McKinsey declined to comment.

The Gupta brothers, who work with Zuma’s son, Duduzane, were accused by South Africa’s anti-corruption watchdog last year of using control over state agencies to siphon public funds.

South Africa’s parliamentary committee on public enterprises is investigating whether McKinsey knowingly let funds from Eskom be diverted to Gupta-controlled firm, Trillian, as a way of securing the deal.

Corruption Watch, a South African anti-graft NGO, is preparing a submission to the U.S. Department of Justice asking it to investigate McKinsey’s dealings with Trillian.