The agency has been mired in controversy about its work for the business, led by the Gupta family, which included a campaign around the issue of 'economic apartheid' and has caused significant offense in South Africa. It is alleged to have been motivated by the Guptas' closeness with the country's president, Jacob Zuma.
Of Henderson (pictured above), Bell said: "He is the chief executive for God’s sake, it's his job to know what is going on." Bell, who left the business in August last year, also said he had warned the agency on multiple occasions that it should not take on the account.
Bell Pottinger initially declined to respond to Bell's comments, but Henderson has since issued a statement to PRWeek.
He said: "We note Lord Bell's comments regarding Oakbay. We completely disagree with his version of events.
"However we currently have a review of our work with Oakbay underway which will set out the key facts; the findings of which will be published in the coming weeks."
At the end of June, PRWeek revealed that Bell Pottinger had taken on a then unnamed law firm to undertake an independent audit of its work with Oakbay.
Henderson had cited the "interim evidence" from Herbert Smith Freehills as the reason for its apology, and the sacking of the partner who it said led on the account.
A Change.org petition asking UK Prime Minister Theresa May to look into Bell Pottinger has gained nearly 13,000 signatures at the time of writing.