Arron Banks, the billionaire businessman who helped fund the pro-Brexit campaign, paid money to a minister in the government of Lesotho only weeks before the country reportedly granted him a diamond mining licence.

Banks has acknowledged paying money in to the private bank account of Thesele Masirebane, a minister in the southern African country’s government but denied it was a bribe.

According to various reports the Brexit backer developed a relationship with Masirebane in 2013 and 2014 – when Banks was seeking permission to search for diamonds in Lesotho. He reportedly paid money to the minister personally, helped fund political campaigning and provided support after a coup in 2014.

In an interview with the BBC, Banks acknowledged making payments to Masirebane. Asked if that was appropriate, he said: “Yes, we were doing a specific job.” He said doing so was “not corruption at all”. Banks said Masirebane was the “minister for women’s equality”, adding he did not “quite see how you link” mining and the minister’s portfolio.

According to Channel 4 News, payments from Banks to Masirebane in South African rand were arranged by the minister’s daughter, Moss Masirebane, in December 2013. In February the following year, she told Banks by email: “My father had meeting with the minister of minings and our application has been approved.” Banks reportedly replied: “Finally – now the fun begins.”

According to the BBC, Banks transferred £65,000 into Maseribane’s personal bank account in South Africa in 2013 and covered the £350,000 cost of his campaign rallies.

Maseribane rejected allegations of bribery or any wrongdoing. He acknowledged to both the BBC and Channel 4 News that he had received money from the British businessman and said he and Banks were good friends.

He told Channel 4 News the reference to “our application” in his daughter’s email did not suggest he was involved in helping Banks gain a prospecting licence for his mine in Lesotho. “‘Our application’ can be implicated in so many ways. The application was, information will be relayed to Arron,” he said.

Maseribane added that he “just wanted to know how far [Banks’] application” had got because the men were friends.

A South African anti-corruption investigator, Paul O’Sullivan, told the BBC he intended to pass a file on the case to the prosecutors in that country, as well as to the UK’s Serious Fraud Office.

“If you are paying the rent, buying food, and financially supporting politicians who could influence and further your own business interests, then there are clear signs of corruption at play,” O’Sullivan said.

“Putting money into the private bank account of a government minister also raises questions. There is a serious lack of transparency. I will be filing a docket, a criminal complaint here in South Africa and I will be sending a file to the Serious Fraud Office in the UK.”

A spokesman for Banks has not responded to the Guardian’s request for comment.

In a statement given to Channel 4 News, Banks said: “Our mining activities in Lesotho were restricted to one licence where we have undertaken exploration work ... We absolutely refute the allegation that payments made to Mr Masirebane were made for granting of any licences. We have made four such applications for licences in Lesotho all of which are outstanding, two years after the original applications, for the very reason we were not prepared to make such payments.”

Kevin Rawlinson

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