Bell Pottinger, the financial public relations firm with several big City names on its client list, cut ties with a company owned by South Africa’s Gupta family, who have been accused of using ties to President Jacob Zuma to influence government decisions.

Oakbay, the holding company of the Guptas’ mining-to-media conglomerate, agreed the termination of the contract just over a week ago.

The resignation followed claims in the South African press that Bell Pottinger was stoking racial tensions in media campaigns to support Mr Zuma and the Guptas.

In a statement on Wednesday Bell Pottinger said that it was ending the relationship after becoming “the target of a politically driven smear campaign in South Africa over the last few months, with a number of totally false and damaging accusations levelled at it.”

Pressure on the firm increased this month after Mr Zuma fired Pravin Gordhan as his finance minister this month, in a divisive reshuffle that triggered a sell-off in the South African rand and sparked the biggest crisis of his presidency.

Opposition parties and allies of Mr Zuma’s ruling African National Congress accused the Guptas of masterminding Mr Gordhan’s replacement to control access to lucrative public contracts. The Guptas and Mr Zuma have always denied the allegations against them.

Bell Pottinger said:

It has been alleged that whilst we were contracted to Oakbay we were primarily working for the Gupta family with the full approval and involvement of President Zuma. This is completely not the case.

Placards bearing pictures of a Bell Pottinger partner involved in the Oakbay contract were brandished in nationwide protests against Mr Zuma last week, including outside the Gupta residence in Johannesburg.

South Africa’s Sunday Times reported last month, citing a report of unknown provenance that has circulated within the ANC, that Bell Pottinger sought to portray opponents of the Guptas as agents of ‘white monopoly capital’.

The firm said “we have never embarked on any of these smearing, racist and politically abusive activities we have been accused of”.

“Our resignation is totally linked to the attacks on us,” James Henderson, Bell Pottinger’s chief executive, said, adding that the firm had begun reviewing the contract late last year.

After his sacking Mr Gordhan told the Financial Times, in a reference to the Guptas, that there had been a campaign “to malign me personally, but more importantly the Treasury, and to pass around disinformation of all sorts”.

Bell Pottinger has lost two high-profile clients with ties to South Africa over their concerns about its contract with Oakbay.

Richemont, the Swiss luxury company headed by South African businessman Johann Rupert, recently ended a 20-year relationship with the firm. Investec, the South African investment group, cut ties last year.

Oakbay has denied being responsible for a campaign using bots on social media which painted Mr Rupert as in league with Mr Gordhan and banks to bring down Mr Zuma.

“I am aware of the attacks, as well as to the identity of the organisers behind the fake accounts. They are experts at disinformation,” Mr Rupert said last year.