A legislator from South Africa's main opposition Democratic Alliance (DA) has accused President Cyril Ramaphosa of sending the state security minister to neighbouring Botswana to try and force that country to drop charges of money laundering and financing a coup attempt against his sister in law, Bridgette Motsepe-Radebe.

Motsepe-Radebe is the sister of Ramaphosa's wife Dr Tshepo Motsepe and is married to ruling African National Congress stalwart and former minister Jeff Radebe. She has denied the charges against her as baseless.

On Wednesday, DA member of parliament Dianne Kohler Barnard said Ramaphosa had sent the state security minister to Botswana to try and strong-arm its President Mokgweetsi Masisi into dropping the case against Motsepe-Radebe.

"Surely the minister of state security, Ayanda Dlodlo, is not paid to protect individual citizens from criminal charges in foreign lands? She is in fact expected to handle matters of state security," she said in a statement.

Taking a swipe at Dlodlo, Kohler Barnard said her department "is in a mess, there are former employees of it sitting in fat positions and facing no consequences despite millions being channelled through their fingers from the Intelligence Slush Fund".

"Yet she is allegedly sent off to take care of his private family matter?" the DA legislator wondered.

The Mail and Guardian newspaper cited an article published last October in Botswana's Sunday Standard which claimed Motsepe-Radebe  and her billionaire brother Patrice Motsepe smuggled R22-million (US$1.3-million) into that country.

The Mail and Guardian said, based on "sanctioned leaks by Botswana’s intelligence agency" the Sunday Standard wrote that the money was given to politician Pelonomi Venson-Moitoi’s campaign to influence the outcome of the ruling Botswana Democratic Party's July elective conference.

According to South Africa's online news outlet IOL, Masisi has pursued the matter and last week his government hired South African advocacy group  AfriForum's Gerrie Nel to help represent it in the case relating to more than US$10-billion allegedly stolen and channelled into accounts in which Motsepe-Radebe was identified as a signatory.

"Our minister of state security is allegedly being sent to wrap him (Masisi) over the knuckles – not for charging our president’s sister in law for financing a coup against him, as one might expect – but for using the wrong attorney," the DA's Kohler Barnard said.

"The point is surely that this is a matter that must be determined before the courts of this sovereign nation. No political finessing should be attempted as a means to sway the outcome, and certainly no South African minister should be sent at taxpayers’ expense to try and do so."

"If Ms Motsepe-Radebe is found guilty, so be it. If she is innocent, so be it. For taxpayers’ money to be utilised to allegedly undermine a legal process in another country is outrageous," Kohler Barnard added.

She said the DA would send a raft of parliamentary questions to the minister of state security to dig out the truth "of this murky situation".

"There are claims the minister of state security, on realising her trip and intentions had been outed, then cancelled. The DA is determined to get to the bottom of this matter. If she lands there, we will know," Kohler Barnard added.