Published: 3:30 PM September 20, 2019 Updated: 6:23 PM September 17, 2020

Leave.EU founder Arron Banks is selling a diamond mine that has been at the centre of hotly-denied claims over the funding of his 2016 Brexit campaign.

Banks confirmed to Channel 4 News that his Newlands mine in the Northern Cape province of South Africa is up for sale for 10m South African rands - just over £500,000.

Banks told Channel 4 News: "Newlands diamond mine was placed in care and maintenance 12 months ago and is up for sale for R10 million (approx. £540k)."

Banks has consistently claimed that the mines were productive and profitable.

A 2014 valuation report commissioned by Banks for investors valued his diamond mines at $79m.

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The report also claimed that the Newlands mine would generate "an annual average net profit of $7m over the mine's 13-year life".

In April 2015 a Diamond Bond offering investors the chance to pump money into the Newlands mine said it would yield diamonds for more than 20 years.

Banks confirmed the mine was for sale after an advertisement for the Newlands mine was posted on Facebook on Tuesday.

The ad says: "Newlands Diamond mine for sale in Barkly West. 400HA farm with Hartsriver front. 5 blows and river exploration yield quality diamonds. Price on request."

Channel 4 News contacted the agent listed in the advertisement, who confirmed the mine was for sale, but refused to give further details without a signed non-disclosure agreement.

Banks told Channel 4 News that he was continuing mining operations at another mine he owns, Blaauwbosch mine.

Banks's diamond mines have been the focus of questions about their profitability and claims they were used to seek funds from Russia, something Banks has consistently denied.

In 2018, Channel 4 News reported that the mines were at the centre of a fierce legal battle between Banks and his former business partner, Chris Kimber.

Court papers filed by Kimber and obtained by Channel 4 News claimed the mines were struggling to meet costs, and that Banks had sought investment from Russia.

Kimber also alleged that money Banks had promised for investment in the mines had been used to fund the Brexit campaign instead.

In March 2019 Channel 4 News then revealed emails and testimony showing Banks and his South African associates had courted a top police general, who they urged to open a criminal investigation into Kimber.

Emails revealed general Kholekile Galawe, the head of the crack Hawks police unit in Kimberley, was offered flights to London, and assistance in obtaining a UK visa.

Galawe told the programme Banks and his associates had also offered him a stake in one of Banks' call centre businesses, in Durban.

At the time of broadcast, Arron Banks denied having had any business dealings with the police chief and claimed the story was a smear.

Banks is currently under investigation by the National Crime Agency. They have confirmed that their probe into the source of the money he used to pay for his Brexit campaign remains "live".

In a statement to Channel 4 News Banks added: "We have consistently denied any Russian involvement in any of our business interests, Brexit-related or otherwise.

"Mr Kimber's statement was lodged after we reported him to the South African police for fraud and there is an outstanding case against him. The South African police have confirmed there is no investigation into myself over any matter."